~ Min.era] urces of t'he Cactu Plain »and East Cact s Plain Wild rness Study Areas, La Paz County, Arizona

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Mineral Resources of the Cactus Plain and East Ca~tus Plain Wilderness Study Areas, La Paz· County, Arizona

By RICHARD M. TOSDAL, ROBERT G. EPPINGER, JAMES A. ERDMAN, WILLIAM F. HANNA, JAMES A. PITKIN, H. RICHARD ·BLANK, JR., RICHARD M. O'LEARY, and . JOHN R. WATTERSON U.S. Geological Survey

TERRY J. KREIDLER U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1704

MINERAL RESOURCES OF WILDERNESS STUDY AREAS: HAVASU REGION, ARIZONA U.S. DEPARTMENT OF THE INTERIOR MANUEL LUJAN, jR., Secretary

U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director

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Library of Congress Cataloging-in-Publication Data

Mineral resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona/ by Richard Tosdal...[et al.]. p. cm.-(Mineral resources of wilderness study areas-Havasu region, Arizona : ch. D) (U.S. Geological Survey bulletin ; 1704-D) Includes bibliographical references. Supt. of Docs. no.: I 19.3:1 704-D 1. Mines and mineral resources-Arizona--Cactus Plain Wilderness. 2. Mines and mineral resources-Arizona-East Cactus Plain Wilderness. 3. Cactus Plain Wilderness (Ariz.) 4. East Cactus Plain Wilderness (Ariz.) I. Tosdal, Richard M. II. Series. Ill. Series: U.S. Geological Survey bulletin ; 1704-D. QE75.B9 no. 1704-D 557.3 s-dc 20 90-14078 [TN24.A] [553'.09791 '72] CIP STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Areas

The Federal Land Policy and Management Act (Public Law 94-579, October 21, 1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral surveys on certain areas to determine the mineral values, if any, that may be present. Results must be made available to the public and be submitted to the President and the Congress. This report presents the results of a mineral survey of the Cactus Plain (AZ-050- 014-NB) and East Cactus Plain (AZ-050-017) Wilderness Study Areas, La Paz County, Arizona. CONTENTS

Summary Dl Absttact Dl Character and setting D1 Mineral resource potential and identified resources DJ Introduction DJ Location and physiography D4 Previous work D4 Methods D4 Acknowledgments D4 Appraisal of identified resources DS Mining activity DS Energy resources D6 Resource appraisal D6 Conclusions DlO Assessment of mineral resource potential DlO Geologic setting DlO Geochemical studies Dll Methods Dl2 Rock, stream-sediment, and heavy-mineral-concentrate samples DIS Creosotebush and paloverde samples D16 Bacillus cereus D17 Interpretation D17 Geophysical studies D18 Gravity data D20 Aeromagnetic data D21 Natural radioelement data D22 Mineral resource potential D23 Base and precious metals D23 Barite and fluorite D23 Manganese D24 Uranium D24 Beryllium D24 Bentonitic clay D24 Sand D24 Oil and gas D24 References cited D2S Appendixes D29 Definition of levels of mineral resource potential and certainty of assessment DJO Resource/reserve classification D31 Geologic time chart D32

FIGURES

1. Index map showing location of Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona D2 2. Map showing mineral resource potential and generalized geology of Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona D8 3. Geochemically anomalous areas in and near Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona D13

Contents V 4. Bouguer gravity anomaly map of Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona, and surrounding region Dl8 5. Residual total-intensity aeromagnetic map of the Whipple, Buckskin, and northern Plomosa Mountains, Arizona and California Dl9 6. Aeromagnetic anomaly map of Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona, and surrounding region D20 7. Aeromagnetic anomaly map of region northwest of lat 34 o N ., long 114 o W. that includes part of Cactus Plain Wilderness Study Area, La Paz County, Arizona D21

TABLES

1. Summary of production data for mineral districts within ihe mining districts in the region surrounding Cactus Plain and East Cactus Plain Wilderness Study Areas DS 2. Geochemical data for samples from Cactus Plain and East Cactus Plain Wilderness Study Areas D7 3. Analytical results for dune-sand samples from Cactus Plain and East Cactus Plain Wilderness Study Areas D7 4. Summary statistics for anomalous concentrations of elements from rock, stream­ sediment, heavy-mineral-concentrate, creosotebush, and paloverde samples; and for Bacillus cereus spore counts from samples collected in and around Cactus Plain and East Cactus Plain Wilderness Study Areas Dl4 ·

VI Contents Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona

By Richard M. Tosdal, Robert G. Eppinger, james A. Erdman, William F. Hanna, James A. Pitkin, H. Richard Blank Jr., Richard M. O'Leary, and John R. Watterson U.S. Geological Survey

Terry J. Kreidler U.S. Bureau of Mines

SUMMARY Plain Wilderness Study Area has moderate resource potential for barite. These same two areas of Cactus Plain Wilderness Abstract Study Area also have moderate resource potential for manga­ nese as well as low resource potential for uranium and beryl­ lium. The entire study area has low resource potential for The Cactus Plain (AZ~SD-014-NB) and East Cactus Plain bentonitic clay. The southern three-quarters of the East Cactus (AZ-050-017) Wilderness Study Areas are in west-central Ari­ Plain Wilderness Study Area and the northern half of the zona, about 4 mi southeast of Parker, Arizona. At the request Cactus Plain Wilderness Study Area have high resource po­ of the U.S. Bureau of Land Management, a mineral survey of tential for sand suitable for foundry, fracturing, and abrasive approximately 79,065 acres was conducted by the U.S. Geo­ uses. The study area has no resource potential for oil and logical Survey and U.S. Bureau of Mines to appraise their gas. identified mineral resources (known) and to assess their mineral resource potential (undiscovered). In this report, "study area .. refers collectively to both wilderness study areas for which a Character and Setting mineral survey was requested by the U.S. Bureau of Land Management. The Cactus Plain (AZ-05()...{)14-A/B) and East Cac­ The southeastern corner of the Cactus Plain Wilderness tus Plain (AZ-05()...{)17) Wilderness Study Areas are ap­ Study Area is within the northern part of the Plomosa mining proximately 4 mi southeast of Parker, Ariz., and include district (Northern Plomosa and Bouse mineral districts). The approximately 79,065 acres of a gentle plain partly covered northeastern corner of the East Cactus Plain Wilderness Study by sand dunes (fig. 1). Isolated bedrock knobs protrude Area is in the Midway mining district. The Cienega and Santa Maria mining districts are within 8 mi and lie north of the above the plains and dunes. Elevations within the study study area. Gold, silver, copper, and minor amounts of lead, area rise from about 700 ft above sea level on the west to zinc, manganese, barite, and fluorite have been produced about 1,500 fi on the east The plain is surrounded by from these districts, though no production is reported from mountain ranges, including the Buckskin Mountains on the mines located within the study area. There are no identified north and northeast, the Bouse Hills on the southeast, and metallic resources in the study area. the Plomosa Mountains on the south. The Colorado River The Cactus Plain and East Cactus Plain Wilderness Study lies about 4 mi to the northwest Ephemeral washes drain Areas have high resource potential for gold, silver, copper, from the study area into Osborne Wash on the north and lead, and zinc. An area in the southeastern part of the Cactus Bouse Wash on the south. The Centtal Arizona Project Plain Wilderness Study Area has high resource potential for Canal separates Cactus Plain Wilderness Study Area from barite and fluorite. Another in the northwestern part of Cactus East Cactus Plain Wilderness Study Area. The study area lies in the highly extended terrane of west-centtal Arizona, immediately west and south of middle Manuscript approved for publication, August 27, 1990. Tertiary metamorphic core complexes (Rehrig and Reynolds,

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 01 1980). Most ranges in this region are fringed by low-angle north and east borders of the study area (fig. 2) and the normal faults of regional extent, known as detachment faults, Plomosa detachment fault that crops out in the northern that accommodated large-scale extensional deformation in Plomosa Mountains along the south border of the Cactus the late Oligocene and Miocene (Davis and others, 1980; Plain Wilderness Study Area. Still farther west, the Moon Spencer and Reynolds, 1986, 1989a, 1989b; Davis, 1988) Mountains detachment fault is exposed on the north flank (see "Appendixes" for geologic time chart). Detachment of the Moon Mountains (fig. 1) and dips northeastward faults near the study area include the Buckskin-Rawhide beneath the western part of the Cactus Plain Wilderness detachment fault that is exposed discontinuously near the Study Area.

WHIPPLE MOUNTAINS

Plain Cactus

APPROXIMATE BOUNDARY 34° ATCHISON OF Oa APPRO~ATEBOUNDARY EAST CACTUS PLAIN OF -···-···-Bouse .. iWILDERNESS STUDY AREA CACTUS PLAIN (AZ-050-017} WILDERNESS STUDY AREA Northern Plomosa (AZ-050-014-NB) mineral district

95

AREA8 OF MAP

0 10MILES

Figure 1. Index map showing location of Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona. Also shown are approximate boundaries of mining districts (dashed lines) as defined by Keith (1978) and their subdivision into mineral districts and subdistricts (patterned areas) by Keith and others (1983a, b) and Spencer and Welty (1989).

02 Mineral Resources of the Wilderness Study Areas: Havasu Region, Arizona Detachment faults divide the bedrock geology of the gathered during this study allow for a mineral resource as­ adjoining mountain ranges into two parts; these are an ex­ sessment of the study area. This assessment does not indi­ tended upper plate of Proterozoic, Paleozoic, Mesozoic, and cate that deposits are actually present or that they are suffi­ Tertiary metamorphic, igneous, and sedimentary rocks and ciently near the surface to be accessible. Only with addi­ a lower plate of Proterozoic, Paleozoic, Mesozoic, and Ter­ tional work can actual deposits be located. tiary metamorphic and igneous rocks. Sedimentation and Geochemical and geophysical data from the study volcanism accompanied extension, and these syntectonic areas indicate that three areas have high resource potential rocks now crop out in the highly faulted upper plate (Davis with a high degree of certainty for gold, silver, copper, and others, 1980; Spencer and Reynolds, 1989b). Exten­ lead, and zinc, whereas the remainder of the study area has sional deformation was followed by basaltic volcanism and high resource potential with a lower degree of certainty for locally silicic volcanism in the Miocene (Davis and others, these elements. The three specific areas lie along the north­ 1980; Suneson and Lucchitta, 1983; Grubensky, 1989). east border of the East Cactus Plain Wilderness Study Area Conglomerate and sandstone are interbedded with and overlie and in the northwestern part and southeastern part of the the basaltic rocks. In the late Miocene and continuing into Cactus Plain Wilderness Study Area. An area in the south­ the Pliocene and perhaps the Pleistocene, the low areas eastern part of Cactus Plain Wilderness Study Area has were flooded by marine waters in which the sedimentary high resource potential for barite and fluorite, and another strata of the Bouse Formation were deposited (Metzger, area in the northwestern part of Cactus Plain Wilderness 1968; Buising, 1987). The Bouse Fonnation, the dominant Study Area has moderate resource potential for barite; these rock unit at the surface in the study area, overlies uncon­ two areas also have moderate resource potential for manga­ fonnably the rocks that underwent extensional deformation nese and low resource potential for uranium and beryllium. in the middle Tertiary. The entire study area has low resource potential for bento­ Detachment faults, associated syntectonic basins, and nitic clay. The southern three-quarters of the East Cactus younger high angle faults are important controls on the dis­ Plain Wilderness Study Area and the northern half of the tribution of mineral resources in the region (Welty and oth­ Cactus Plain Wilderness Study Area have high resource ers, 1985; Spencer and Welty, 1986, 1989). Mineral explo­ potential for sand suitable for foundry, fracturing, and abra­ ration in western Arizona and southeastern California has sive uses. The entire study area has no resource potential demonstrated the association of these rocks and geologic for oil and gas. · No identified resources are present in the structures to various types of deposits (Sherbourne and oth­ study area. ers, 1979; ·Wilkins and Heidrick, 1982; Wilkins and others, 1986; Spencer and others, 1988; Wilkinson and others, 1988; Lehman and Spencer, 1989). In the Cactus Plain and East INTRODUCTION Cactus Plain Wilderness Study Areas, the Miocene basalt, the Bouse Fonnation, and the Quaternary eolian and alluvial This mineral survey was requested by the U.S. Bureau deposits unconformably overlie the highly extended terrane of Land Management and is the result of a cooperative effort and effectively conceal any metallic deposits that may be by the U.S. Geological Survey and the U.S. Bureau of Mines. present An introduction to the wilderness review process, mineral survey methods, and agency responsibilities was provided by Beikman and others (1983). The U.S. Bureau of Mines Mineral Resource Potential and Identified evaluates identified resources at individual mines and known Resources mineralized areas by collecting data on current and past mining activities and through field examination of mines, Most of the mineral deposits in the region of the Cac­ prospects, claims, and mineralized areas. Identified resources tus Plain and East Cactus Plain Wilderness Study Areas are are classified according to a system that is a modification of located within the intensely faulted rocks that lie in the that described by McKelvey (1972) and U.S. Bureau of upper plates of detachment faults (Spencer and Welty, 1989). Mines and U.S. Geological Survey (1980). U.S. Geological Less common metallic deposits are found in the mylonitic Survey studies are designed to provide a scientific basis for rock of the lower plate close·to the detachment fault (Spen­ assessing the potential for undiscovered mineral resources cer and Welty, 1989). Upper and lower plate rocks are by detennining geologic units and structures, possible envi­ buried beneath the unconfonnably overlying late Tertiary ronments of mineral deposition, presence of geochemical and sedimentary and volcanic rocks in the study area. This geophysical anomalies, and applicable ore-deposit models. extensive cover hinders the assessment of mineral resource Goudarzi ( 1984) discussed mineral assessment methodology potential of the study area. Despite this limitation, the pro­ and tenninology as they apply to these surveys. Definition jection of structures and rock types into the study area, the of levels of mineral resource potential and certainty of as­ knowledge of the location of deposits in the region, past sessment and the resource/reserve classification are included mining activity, and the geochemical and geophysical data in the "Appendixes."

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 03 Location and Physiography was ftrst studied by Metzger (1968) as part of a hydrologic study of the Colomdo River area (Metzger and others, 1973). The Cactus Plain (AZ-050--014-A/B) and East Cac­ Buising (1987) defined the stratigraphy and paleoenviron­ tus Plain (~50--017) Wilderness Study Areas are ap­ ment of the Bouse Formation in more detail. proximately 4 mi southeast of Parker, Ariz., and include Keith (1978), Keith and others (1983a, b), and Spen­ approximately 79,065 acres on a gentle plain. Isolated bed­ cer and Welty (1989) defined the mining and mineral dis­ rock knobs protrude above the plain. Elevations within the tricts throughout the region and their nomenclature is used study areas rise from about 700 ft above sea level on the herein. Areas outside the study area have been explored for west to about 1,500 ft on the east. The plain is surrounded precious metal and uranium-vanadium deposits (Sherbourne by mountain ranges, including the Buckskin Mountains on and others, 1979; Wilkins and Heidrick, 1982; Wilkins and the north and northeast, Bouse Hills on the southeast, and others, 1986; Spencer and others, 1988; Lehman and Spen­ Plomosa Mountains on the south. The Colorado River lies cer, 1989) and the results of this work are applicable to the some 4 mi to the northwest (fig. 1). Ephememl washes mineral resource potential of the study area. drain from the study area into Osborne Wash on the north border and Bouse Wash on the south border. The Central Arizona Project Canal separates Cactus Plain Wilderness Study Area on the west from East Cactus Plain Wilderness Methods Study Area on the east Access to the Cactus Plain Wilderness Study Area is The U.S. Geological Survey conducted detailed field from Arizona Highway 72 on the south, a poorly main­ investigations of the Cactus Plain and East Cactus Plain tained sand road that parallels a powerline along the west Wilderness Study Areas in 1986 and 1988. This work in­ border, a paved road along Osborne Wash on the north, the cluded geologic mapping at scales of 1:24,000, geochemi­ service road for the Central Arizona Project Canal along cal sampling, and the examination of outcrops for evidence the northeast, and from maintained dirt roads between Bouse of mineralization. The geochemical survey, conducted be­ and Swansea along the southeast border of the study area tween September 21 and 27, 1988, included collection of (fig. 1). The Atchison, Topeka, and Santa Fe Railroad rocks and stream sediments from areas of bedrock older borders the Cactus Plain Wilderness Study Area on the south. than the Bouse Formation and Quaternary eolian deposits, Access to the East Cactus Plain Wilderness Study Area is the sedimentary rocks and deposits that cover m.uch of the also from the service road for the Central Arizona Project study area. Biogeochemical sampling in areas of the younger Canal along the southwest, from maintained dirt roads be­ sedimentary rock and deposits was necessary for assessing tween Bouse and Swansea on the southeast and between the possibility of buried metallic deposits beneath these units. the Osborne Wash road and Swansea on the north, and by a Available regional gravity, aeromagnetic, and aerial gamma­ service road to a powerline along the northeast border ray spectrometry surveys were also used in the assessment (fig. 1). U.S. Bmeau of Mines personnel obtained minerals information from published and unpublished literature, U.S. Bureau of Mines files, and mining claim and oil and gas Previous Work lease records at the U.S. Bureau of Land Management State Office in Phoenix. Fieldwork consisted of a search for mines and prospects and the examining and sampling rock Early descriptions of the rock types and various min­ outcrops and unpatented mining claims in and near the study eral deposits in the region are found in Lee (1908), Bancroft area. (1911), and Jones and Ransome (1920). Jemmet (1966) mapped the northern Plomosa Mountains. Fernandez (1965) and Zambrano (1965) studied mines in the Buckskin Moun­ tains immediately north of the study area. Geologists from Acknowledgments the Arizona Geological Survey have studied the geology and setting of the mineral occurrences in the region (Keith, This work was supported by the National Mineral 1978; Scarborough and Wilt, 1979; Keith and others, 1983a, Resource Assessment Program of the U.S. Geological b; Welty and others, 1985; Spencer and Welty, 1986, 1989; Survey. Discussions with the J .E. Spencer and SJ. Reynolds Spencer and Reynolds, 1989a; Grubensky, 1989) and their of the Arizona Geological Survey improved our understand­ work has been invaluable for this study. Field studies of ing of the geology of the area. J .E. Spencer kindly provided extensional deformation in the Whipple Mountains and parts his geologic mapping of the Buckskin Mountains for use in of the Buckskin Mountains are also important sources of this report. Special thanks are extended to Tom Peacock information (Davis and others, 1980; Frost, 1981, 1983; for preparation of plant samples for geochemical analysis Marshak and VanderMeulen, 1989). The Bouse Formation and to Diana Mangan for preparation of the figures.

04 Mineral Resources of the Wilderness Study Areas: Havasu Region, Arizona \ APPRAISAL OF IDENTIFIED RESOURCES suitability for glass manufacture and other industrial uses. Kreidler (1986, 1987) presents more detail on most aspects By Terry J. Kreidler of this study. Complete analytical data are available for U.S. Bureau of Mines inspection at the U.S. Bureau of Mines, Intermountain Field Operations Center, Building 20, Denver Federal Center, U.S. Bureau of Mines personnel reviewed sources of Denver, CO 80225. minerals information, including published and unpublished literature, U.S. Bureau of Mines files, and mining claim and oil and gas lease records at the U.S. Bureau of Land Mining Activity Management State Office in Phoenix. Discussions on the mineral resources of the study areas were held with U.S. The Cactus Plain and· East Cactus Plain Wilderness Bureau of Land Management personnel at the District Of­ Study Areas are surrounded by four mining districts (table fice in Yuma and the resource area office in Lake Havasu 1, fig. 1). The northeastern comer of the East Cactus Plain City, Ariz. Wilderness Study Area is in the Midway mining district. Fieldwork, completed in 16 employee-days, consisted This district contains gold, silver, and copper in spotty de­ of examining and sampling rock outcrops and unpatented posits along faults and fractures in mylonitic gneiss, schist, mining claims in and near the study area. Thirteen samples marble, and calc-silicate rocks of Proterozoic and Mesozoic were taken: eight rocks, two stream sediment, one panned protolith age. The Cienega mining district (7 .5 mi north of concenttate, and two dune sand. Six samples were ana­ Cactus Plain Wilderness Study Area) produced gold, silver, lyzed for gold and silver by frre assay and six by inductively copper, and minor amounts of lead from ore occurring as coupled plasma-atomic emission spectroscopy for copper, replacement deposits in weakly metamorphosed Paleozoic lead, zinc, barium, and arsenic. The dune-sand samples and Mesozoic limestone, shale, and quartzites, which struc­ were analyzed for silica and other elements that affect the turally underlie Proterozoic gneiss in places. The Santa

Table 1. Summary of production data for mineral districts within the mining districts in the region surrounding Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona [Data from Keith (1978), Keith and others (1983b), and Spencer and Welty (1989). Gold and silver given in troy ounces, copper, lead, and zinc given in short tons of ore. Mn, manganese;-, not applicable]

Production data Mineral When district active Gold Silver Copper lead Zinc Other Clenega mining dlstrld

Cienega ..... 1880-1969 12,011 1.596 857 Mammon ... 1880-1969 60 142 42.5 Pride ...... 1911-1912 100 4,000 0.01

Midway mining district

Midway ..... Early 1900's 45 35 4.7 to present.

Plomosa mining dlstrld

Plomosa .... Intermittently 25,000 129,200 526 344 65 since 1860's. Bouse ...... 1928-1930 100 6.5 9,000 tons Mn; 2,700 tons barite. Santa Marla mining district

Clara...... Intermittently 35 1,738 2,335 early 1900-1955. Planet ...... Intermittently 317 268 9,752 since 1860's. Swansea .... Intermittently 507 33,112 13,200 400 tons since 1860's. Mnore.

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona OS Maria mining district (5 mi north of East Cactus Plain Wil­ theory has had negative results (Reif and Robinson, 1981). derness Study Area) produced gold, silver, and copper from As of September 1986, the leases in the study area had not ore in massive to lensing iron-oxide replacement bodies in been drilled ot tested, but in 1985, Petty-Ray Geophysical Paleozoic and Mesozoic metasedimentary rocks. The Plo­ Co. ran a seismic line a. few miles north and east of the mosa mining district includes the Black Mountain mine, area; the results of the survey are proprietary. which lies adjacent to the southern part of Cactus Plain Wilderness Study Area, and base- and precious-metal mines in the northern Plomosa Mountains, a few miles south. The Resource Appraisal district produced gold, silver, copper, lead, .zinc, manga­ nese, and barite from veins and irregular bodies in Paleo­ No metallic mineral resources were identified in the zoic and Mesozoic sedimentary rocks and Tertiary volcanic study area. The middle Tertiary and older rocks that crop and sedimentary rocks. As of June 1990, mines within 4 to out in the study area are only sparsely mineralized. Samples 5 mi of the study area were inactive. However, the Copper­ taken in and near the study area contain insignificant amounts stone mine, some 10 mi southwest of Cactus Plain Wilder­ of gol~ silver, copper, lead, and zinc, except for one sample, ness Study Area, is active and is one of the largest produc­ which is from Tertiary sandstone and conglomerate on the ing gold mines in Arizona (Spencer and others, 1988). flank of Black Peak outside the northwest corner of the A mining district is delineated on the basis of mineral Cactus Plain Wilderness Study Area. This sample (table 2, occurrence locations and most production records and early sample 1) contains concentrations of lead and zinc several literature use these districts as a means of categorizing in­ times the background level. formation. Keith and others (1983b) arranged the mineral At the Green Streak mine, about 1 mi northeast of the occurrences of Arizona into mineral districts on the basis of East Cactus Plain Wilderness Study Area (fig. 2), oxidized geologic criteria of metallogenic systems of similar age and copper minerals occur locally in a quartz vein, trending N. style of mineralization. A single mining district may con­ 35" W. and dipping 55" NE., in gneiss and schist in the lower tain more than one mineral district. The Cienega mining plate of the Buckskin-Rawhide detachment fault. Work­ district, for example, includes the Cienega, Mammon, and ings consist of two shafts, about 35 ft and 100ft deep, an · Pride mineral districts; the Santa Maria mining district in­ adit, and several prospect pits and trenches; the mine ac­ cludes the Clara, Planet, and Swansea mineral districts; the counts for nearly all the recorded production from the Mid­ Plomosa mining district includes the Northern Plomosa and way district Samples from the mine area contain 0.74 to Bouse mineral districts; the Midway mining district includes greater than 2 weight percent (or 7,443 to greater than 20,000 the Green Streak subdistrict of the Midway mineral district. parts per million, ppm) copper and 0.4 to 1.87 ppm gold, See figure 1 for location of mining and mineral districts. and anomalous concentrations of silver (table 2). Because Mining claims have been located near the study area of the spotty, discontinuous nature of the mineralized rock, in the Cienega, Midway, and Plomosa mining districts, and no base- or precious-metal resource was identified. Barium at least eight claims have been staked on Black Peak, 1 mi concentrations in the three mine samples are 0.15 to greater northwest of Cactus Plain Wilderness Study Area. U.S. than 3 weight percent or 1,500 to greater than 30,000 ppm Bureau of Land Management claim records list 15 (table 2) higher than the average of 425 ppm (0.043 weight unpatented claims that are in the Cactus Plain Wilderness percent) for metamorphic rocks (Levinson, 1980, p. 865). Study Area. As of September 1987, no claims were located No barite, a barium mineral, was identified. in the East Cactus Plain Wilderness Study Area. No visible In the Cactus Plain Wilderness Study Area, barium evidence of any recent mining activity was found on any of and arsenic values in the three basalt and two sandstone the claims. samples are higher than average for their respective rock types. Sample values (table 2) ranged from 1,200 to 8,000 ppm barium and 30 to 50 ppm arsenic (the 130 ppm value Energy Resources for sample 7 is suspect). Average contents for similar rock types are: barium, 250 ppm for basalt and 10 to 100 ppm About 50,000 acres of the study area are covered by for sandstone; arsenic, 2 ppm for basalt and 1 ppm for oil and gas leases. Ryder (1983, p. C19), however, rates sandstone (Levinson, 1980, p. 864-865). the oil and gas resource potential of the study areas as low Barium is highly mobile in mineralizing systems and because the organic richness, reservoir quality, and thermal is commonly associated with lead-zinc-silver deposits; its history of the rocks are not conducive to the formation of distribution often extends several miles from a deposit significant volumes of hydrocarbons. The leasing is prob­ (Levinson, 1980, p. 865). In the northern part of the Plo­ ably a result of speculation that the hydrocarbon-rich over­ mosa mining district, barite is a common by-product in the thrust belt, which produces large quantities of oil and gas in silver-copper-lead-zinc ores and is found with fluorite in Wyoming, extends southward into Arizona (Keith, 1979, p. volcanic agglomerate at the Black Mountain mine adjacent 10). To date, all exploratory drilling in Arizona testing this to the southeastern part of the Cactus Plain Wilderness Study

06 Mineral Resources of the Wilderness Study Areas: Havasu Region, Arizona Table 2. Geochemical data for samples from Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona [Gold and silver determined by fire assay, all other elements by inductively coupled plasma-atomic emission spectroscopy. -, not detected; na, not analyzed; <,less than given value; ppm, parts per million; ppb, parts per billion. Complete analytical tables and location of samples are available in Kreidler (1986, 1987)]

Sample Au Ag Cu Pb Zn 8a As no. (ppbJ {ppm) Description Stream-sediment and roek samples

na na 30 400 500 3,700 50 Iron-stained sandstone and conglomerate; collected on flank of Black Peak.

3 na na 7.9 32 180 8,000 30 Iron-stained sandstone and conglomerate.

4 3,500 na na na na na Material from wash draining east side of Black Peak.

6 na na 41 <10 120 3,700 32 Scoriaceous basalt. capped by limestone.

7 na na 21 27 31 6,200 130. Do.

8 na na 6.9 <10 170 1,200 30 Do. Green Streak mine

1 608 1,500 7,443 7 72 1.500 select

2 400 6.400 >20,000 9 78 >30,000 3 chip

3 1,870 600 15,392 56 107 25,500 4 select

Area (fig. 2). Thus, the barium enrichment described previ­ Table 3. Analytical results for the dune-sand samples from ously could be an alteration halo related to the mineraliza­ Cactus Plain (CP) and East Cactus Plain (ECP) Wilderness tion that took place in the Plomosa mining district No Study Areas, La Paz County, Arizona [See figure 3 for definition of element symbols and text for definition of evidence of a barite deposit was found in the study area. chemical compounds. All detenninations by inductively coupled plasma­ Arsenic is also associated with deposits of gold, sil­ atomic emission spectroscopy. See Kreidler (1986, 1987) for analytical ver, copper, and zinc (Levinson, 1980, p. 864-865), all of descriptions and location of samples] which have been produced from · the nearby mining dis­ tricts, particularly the Plomosa mining district As with Si0 Al 0l Fe 0l Cr Co Ti Sample 2 2 2 barium, arsenic enrichment is probably an alteration halo type percent parts per million the in surrounding deposits the northern Plomosa Moun­ CP 90.2 4.5 1.6 180 9.1 1,200 tains and possibly those in the other districts as well.· The barium and arsenic alteration patterns could also ECP 88.7 4.6 1.3 <50 <10 1,700 indicate that base- and precious-metal deposits are concealed beneath the Bouse Formation in the study area. Extensive Average 98.5 0.1 .02 6 <2 150 glass sand1 and costly subsurface exploration would be necessary to test this conjecture. 1Fran Coope and Harben, 1977, p. 16. Analyses of two dune-sand samples from the study area showed it to be unsuitable for use in glass production because of low silica (Si0 ) and high iron (Fe 0~, chro­ (1960, p. 99-103). Sand is a high-volume, low-unit-value 2 2 mium (Cr), and aluminum (~0:) content (table 3). The commodity and transportation costs are a major factor in its sand is, however, suitable for use as foundry, fracturing, economic development. Without a local market, the sand is and abrasive sand according to criteria described by Bates not likely to be developed.

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 07 m Area having high mineral resource potential (H) Ag Co~:ties F Fluorite D Area having high mineral resource potential (H) for sand Au Gold Mn Manganese 17'""71 . Ba Barite U Uranium ~ Area having moderate mineral resource potential (M) BC Bentonitic clay Pb Lead Be Beryllium S Sand D Area having low mineral resource potential (L) Cu Copper Zn Zinc

Levels of certainty of assessment Mines and prospects-See text for discussion B Data only suggest level of potential 1 Green Streak mine 4 New Standard mine ' C Data give good indication of level of potential 2 Black Mountain mine 5 Little Golden prospect D Data clearly define level of potential 3 Pridemine Continued on next page

08 Figure 2. Mineral resource potential and generalized geology (mapped by R.M. Tosdal, 1986) of Cactus Plain and East Cactus (1989), and Marshak and others (1987). Geology of Plomosa Mountains modified from Jemmet (1966). Base from U.S. Geological Plain Wilderness Study Areas. Geology of Buckskin Mountains modified from j.E. Spencer (unpub. data, 1987), Grubensky 09 Survey, 1:62,500, Black Peak, 1959; Bouse, Utting, 1962; Swansea, 1966. Contour intervals, 20, 40, and 80ft. EXPLANATION-Continued Conclusions Geologic map units Qal Alluvium (Quaternary}-Unconsolidated deposits of sand, silt, and Neither the Cactus Plain nor the East Cactus Plain gravel in washes and on piedmonts to the west and east of the Plomosa Mountains Wilderness Study Area contains known or identified metal­ Qs Sand and gravel (Quaternary}-Unconsolidated deposits of sand, lic mineral resources. Rocks in the study area contain gravel, and silt in washes anomalous concentrations of barium and, to a lesser extent, Ot Talus deposits (Quaternary}-Unconsolidated to semiconsolidated talus deposits composed of locally derived gravel and sand; found arsenic. Barite has been mined just south of the study area primarily around Black Peak and is an acceSsory mineral in ores from the Plomosa min­ Qg Lag gravel (Quaternary}-Unconsolidated pebble to cobble gravel lag deposits on wash terraces in western parts of Cactus Plain. ing district, but no evidence for a barite deposit was found Clasts consist largely of mylonite and gneiss from the Buckskin in the study area. Arsenic, as well as barium, can be used Mountains as a pathfmder element for deposits of gold, silver, copper, Qe Eolian sand (Quaternary)-Fine-grained sand forming partly stabilized dunes and zinc, all of which occur north and south of the study QTc Conglomerate and sandstone (Quaternary and Tertiary?}­ area and may underlie the eolian deposits and the subjacent Semiconsolidated conglomerate, fanglomerate, sandstone, and Bouse Formation, but the requisite subsurface data are lack-. siltstone veneers on piedmonts, talus, and fan deposits at edges of bedrock exposures and older deposits ing. The sand is usable in foundry, fracturing, and abrasive Tbo Bouse Formation (Pliocene and Miocene}-Sandstone, siltstone, purposes, but this high-volume, low-unit-value commodity limestone, conglomerate, tuffaceous sandstone, and rare deposits of tufa. On west part of Cactus Plain, unit is covered by a thin can not be shipped any distance profitably. veneer of eolian sand (Qe) and lag gravel (Qg) Tba Basalt and agglomerate (Miocene)-Olivine basalt and plagioclase megaporphyritic basalt flows, agglomerate, and cinders. Unconformably overlain by the Bouse Formation (Tbo). ASSESSMENT OF MINERAL RESOURCE Present only in the middle of Cactus Plain; its relationship to POTENTIAL other volcanic units in adjoining ranges is unknown. Forms morphologically distinct cinder cones Tt Trachyte and rhyolite tuffs (Miocene)-Interbedded trachytic lava By Richard M. Tosdal, Robert G. Eppinger, james A. flows, lithic-lapilli rhyolitic tuff, hypabyssal intrusions, and Erdman, William F. Hanna, James A. Pitkin, H. Richard basalt flows (Grubensky, 1989) Tb Basalt (Miocene)-Dark-gray and black basalt flows and minor Blank, Jr., Richard M. O'Leary, and John R. Watterson dikes. Rocks are gently tilted to subhorizontal and U.S. Geological Survey unconformably overlie steeply tilted strata Tc Carbonate rocks (Tertiary)-Massive medium- to dark-brown ferroan carbonate rocks in replacement deposits in Proterozoic and Paleozoic rocks along detachment faults Geologic Setting Tvs Sedimentary and volcanic rocks (Miocene and (or) Oligocene}- lnterbedded sandstone, conglomerate, breccia, mudstone, The Cactus Plain and East Cactus Plain Wilderness limestone, and tuffaceous rocks. Locally contains beds of dark andesitic lava flows Study Areas lie in the highly extended terrane of west­ Mzs Metasedimentary and volcanic rocks (Mesozoic}-Quartzite, central Arizona immediately west and south of middle Ter­ calcareous quartzite, phyllite, and quartz blastophenocrystic schist tiary metamorphic core complexes (Rehrig and Reynolds, Pzq Quartzite and marble (Paleozoic)-Tan and greenish quartzite and 1980). Most ranges in this region are fringed along the minor amounts of micaceous quartzite, bluish-gray marble, and range-basin interface by low-angle normal faults of regional orange-brown dolomitic marble E?Q Granite (Proterozoic)-Medium- to coarse-grained porphyritic extent, known as detachment faults, that accommodated granite large-scale extensional deformation in the late Oligocene gm Granite and metamorphic rocks (Tertiary, Mesozoic, and and Miocene (Davis and others, 1980; Spencer and Reynolds, Proterozoic}-Leucocratic hornblende-bearing biotite granite and granodiorite, medium- to coarse-grained leucogranite gneiss, 1986, 1989b, c; Davis, 1988). Detachment faults near the amphibolite, and locally abundant northwest-trending mafic and study area include the Buckskin-Rawhide detachment fault silicic dikes g g Gneiss (Tertiary, Mesozoic, and Proterozoic )-Predominantly exposed discontinuously near the north and east borders of layered mafic and quartzofeldspathic gneiss and pegmatite. Most the study area (fig. 2) and the Plomosa detachment fault in of the gneiss has plutonic protoliths of several ages. Unit may the northern Plomosa Mountains near the south border of also include some unmapped metasedimentary rocks (Mzs, Pzq). Gneissosity locally overprinted by subhorizontal mylonitic the Cactus Plain Wilderness Study Area. Still farther west fabrics. Present in the lower plate of the Buckskin-Rawhide is the Moon Mountains detachment fault that projects un­ detachment fault derneath the western part of the Cactus Plain Wilderness Contact Study Area. Detachment faults divide the bedrock geology of the -.--·· Fault-Steeply to moderately dipping; dashed where approximately located; dotted where concealed; bar and ball on downthrown side adjoining mountain ranges into two parts: an extended up­ per plate of Proterozoic, Paleozoic, Mesozoic, and Tertiary

-ll-IJ.. ... Detachment fault-Low-angle normal fault; dotted where concealed. metamorphic, igneous, and sedimentary rocks and a lower Ticks on upper plate plate of Proterozoic, Paleozoic, Mesozoic, and Tertiary metamorphic and igneous rocks. Extensional deformation Figure 2. Explanation continued. resulted in a penetrative subhorizontal mylonitic fabric in

010 the lower plate rocks in the Buckskin Mountains. Sedimen­ where they have been included in the Osborne Wash For­ tation and volcanism accompanied extension, and these mation of Davis and others (1980) by Grubensky (1989). syntectonic rocks unconformably overlie Mesozoic and older The megaporphyritic basalts may be broadly correlative with rocks in the highly faulted upper plate (Spencer and late Miocene megacrystic basalts found elsewhere in the Reynolds, 1989c). The middle Tertiary volcanic and sedi­ region (Suneson and Lucchitta, 1979, 1983). , mentary rocks usually consist of fanglomerate, sandstone, In the late Miocene(?) and continuing into the Plio­ local lacustrine limestone, andesitic volcanic flows and ag­ cene and perhaps the Pleistocene, low areas were flooded glomerates, and silicic ash flows. Monomictic and by marine waters in which the sedimentary strata of the polymictic breccias and conglomerates are locally interbed­ Bouse Formation were deposited (Metzger, 1968; Buising, ded with volcanic and sedimentary rocks and these are likely 1987). Fine-grained sandstone, limestone, and siltstones fault-scarp deposits along normal faults above the detach­ make up the Bouse Formation. Conglomerate and coarse ment fault. sandstone facies of the formation are adjacent to bedrock This extended terrane is present above the alluviated and represent talus and fan deposits (Buising, 1987). Cal­ basins as a series of northeast-trending antiformal and syn­ careous tufa deposits, a distinctive rock type of the Bouse formal culminations that plunge beneath the alluvial cover Formation (Metzger, 1968), cap most of the bedrock knobs in the study area (Spencer and Reynolds, 1989b). Lower in the Cactus Plain Wilderness Study Area. The Bouse plate mylonitic rocks form the antiforms and faulted upper Formation is the dominant unit at the surface in the study plate rocks occupy the synforms. Most of the metallic area. About 500 ft of the Bouse Formation overlies upper mineral deposits in the Buckskin Mountains are found in Miocene conglomerate in the lower part of a 1,000-ft-deep the synforms (Spencer and Welty, 1989). drill hole immediately west of the study area (Metzger, Outcrops of bedrock affected by extensional defor­ 1968); post-Bouse Formation sedimentary rock, including mation are sparse within the study area. In the northwest­ deposits of the Colorado River, are in the top few hundred ern part of the Cactus Plain Wilderness Study Area, several feet of the drill hole. The Bouse Formation thins to the east knobs above the surrounding younger sedimentary rocks across the study area toward the southwestern Buckskin consist of Paleozoic marble and micaceous quartzite that Mountains. are faulted against Tertiary megabreccia. This fault con­ During the Pleistocene and the Holocene, the Colo­ tains specularite and carbonate cement The knobs along rado River drainage formed. Tributary washes were estab­ the south border of the Cactus Plain Wilderness Study Area lished across the region and eolian deposits developed on are Miocene limestone, sandstone, andesite, and megabrec­ the broad interfluvial plains. Eolian deposits dominate the cia and Paleozoic marble that represent the highly faulted northern part of the Cactus Plain Wilderness Study Area upper plate of the Plomosa detachment faulL Mylonitic and most of the East Cactus Plain Wilderness Study Area. gneiss of the lower plate crops out along the northeast border The eolian deposits are probably no more that a few tens of of East Cactus Plain Wilderness Study Area. feet thick. Extensional deformation in the region was followed by basaltic volcanism and local silicic volcanism in the Miocene (Suneson and Lucchitta, 1979, 1983, Grubensky, Geochemical Studies 1989). Conglomerate and sandstone deposited in alluvial fan environments are interbedded with the volcanic rocks. A reconnaissance geochemical survey of the Cactus These rocks are referred to as the Osborne Wash Formation Plain and East Cactus Plain Wilderness Study Areas was of Davis and others (1980) and as mesa-forming basalts by conducted in 1988 to locate altered, mineralized, or goo­ Suneson and Lucchitta (1983). In the western Buckskin chemically anomalous areas but was not designed to find Mountains north of the Cactus Plain Wilderness Study Area, individual mineral deposits. Because of the sparse outcrops the postdetachment volcanic and sedimentary rocks are more (less than one percent exposure) and extensive alluvial and than 600 ft thick, dip slightly southwest, and are cut by eolian cover in the study area, this geochemical survey con­ northwest-trending high-angle faults (Davis and others, 1980; sisted of two parts. One part followed the conventional Grubensky, 1989; Spencer, 1989). geochemical approach that uses stream sediments, heavy­ Basalt crops out locally in the central part of the Cac­ mineral concentrates, and rock samples. Forty-eight rocks, tus Plain Wilderness Study Area where it is present in two 18 stream sediments, and 20 heavy-mineral concentrates forms: fine-grained flows that form linear ridges, and were collected in outcrops of pre-Bouse Formation rock megaporphyritic lavas, cinders, and agglomerates that make inside the study area. The second part consisted of a bio­ up morphologically distinct cinder cones above the sur­ geochemical reconnaissance survey, which augmented rounding and onlapping sedimentary rocks of the Bouse the scant data base from the conventional approach by pro­ Formation. The fine-grained basalts probably are correla­ viding information on soluble metals that are available at tive with the gently tilted Miocene basalts on the prominent depths of less than 70 ft or that are present in the direction mesas north of the Cactus Plain Wilderness Study Area, from which the ground water flows. Biogeochemical

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 011 exploration surveys broadly similar to this one have proven microscopically; and then pulverized for chemical analysis successful in exploration for disseminated gold prospects (Eppinger, 1990a, b). beneath basin fill in Nevada and in China in areas wholly Vegetation samples generally were collected from covered with eolian sands (Lovering and McCarthy, 1978; shallow arroyos or washes (Eppinger, 1990a, b). For Li and others, 1989). creosotebush, branch-tip samples stripped by hand from three For the biogeochemical study, samples of creosotebush adjacent shrubs were composited into a single sample at (Larrea tridentala [OC.] Coville) and two species of palo­ each site. These samples were predominantly leaf tissue ver~e, blue paloverde (Cercidium floridum Benth.) and with some admixture of fme twigs. Of the two paloverde little-leaf, or foothill, paloverde (C. microphyllum [Torr.] tree species, neither is as wid~spread as creosotebush. How­ Rose and Johnston) were collected and analyzed, where ever, at least one of the two paloverde species was sampled possible, from 80 sites within and around the study area. at most sites. Single paloverde trees were sampled at each Creosotebush, a shallow-rooted desert plant, was most useful site, and the samples consisted of branch ends about 8-in. because of its widespread distribution and its effectiveness long. For the more riparian blue paloverde, leaves and for detecting gold anomalies in areas with as much as 70 ft stems were combined, but for the more drought tolerant of colluvial cover in desert regions (Busche, 1989). The little-leaf paloverde, samples consisted almost entirely of more deeply rooted plants such as paloverde, particularly stem material because the leaves appear only after signifi­ blue paloverde, also absorb metals from ground water and cant rainfall. Blue paloverde was found at 42 sites and accumulate them in various above-ground parts (Chaffee, little-leaf paloverde was found at 36 sites. Five extra samples 1976, 1977). These plants can indicate local mineralized of creosotebush were collected along mineralized faults and ground in areas where no evidence appears in the overbur­ shear zon'es, and multiple samples were collected at several den (Cohen and others, 1987). In this study, however, metal of the mines and prospects outside the study area. For both anomalies in creosotebush probably indicate the more local plant and soil samples for B. cereus assays, duplicate mineralized sources than do anomalies in paloverde, be­ samples were collected at 10 sites to assess the site variabil­ cause the shallow-rooted creosotebush does not reflect re­ ity; one of the duplicate samples from these sites was later gional ground-water geochemistry ·to the extent that the split after the sample was milled to estimate analytical pre­ deep-rooted paloverdes do. cision. Soil samples also were collected at the 80 vegetation For B. cereus spore counts, surface soil was sampled sample sites to determine the spore content of the bacte­ from a single pit at each site. The top 1.25-in. layer of soil rium Bacillus cereus. The discovery of B. cereus spore was sieved through a 30-mesh screen. The minus-30-mesh population anomalies and the original study of its ecology fraction was later further sieved through a 60-mesh screen in mineralized soil are discussed by Watterson and others and the B. cereus count was estimated using the fme frac­ (1986). These initial fmdings were the basis for further tion. The B. cereus spore determinations were made in U.S. investigation on the potential use of B. cereus in mineral Geological Survey laboratories following the method out­ exploration, particularly near gold deposits (Parduhn and lined by Watterson (1985). others, 1986; Parduhn, 1987). Stream-sediment, heavy-mineral-concentrate, and rock samples were analyzed for 35 elements by semiquantitative emission spectrography (Grimes and Marranzino, 1968)~ In addition, stream sediments and rocks were analyzed for ar­ Methods senic, bismuth, cadmium, antimony, and zinc by the more sensitive atomic-absorption and inductively coupled plasma­ Stream-sediment samples, representing a composite atomic emission spectroscopy (ICP-AES) methods (Crock of rock and soil exposed in the drainage basin, were col­ and others, 1987; Motooka, 1988). Stream-sediment and hited from small active alluvial channels draining bedrock rock samples were analyzed for low-level gold (detection and were sieved and pulverized for chemical analysis limit: 50 parts per billion (ppb) for stream sediments, 2 ppb (Eppinger, 1990a, b). From each site, additional heavy­ for rocks) by graphite-furnace atomic absorptioq (GFAA) mineral-concentrate samples were collected and separated methods (Thompson and others, 1968; Meier, 198p). in the laboratory into three fractions using an electromag­ Plant samples were washed, milled, ashed; ~id-di­ net: a magnetic, slightly magnetic, and nonmagnetic fraction. gested, and the solutions analyzed by three techniques: ICP­ Nonmagnetic fractions commonly contain the primary and AES, GFAA, and ICP-AES with an organic extraction by secondary ore minerals, and this fraction was examined for diisobutyl ketone (ICP-AES/DIBK). A 100-mg (milligram) mineralogical content by microscopic and X-ray diffraction aliquot of each sample was analyzed by ICP-AES (Crock methods. Nonmagnetic and slightly magnetic fractions were and others, 1987) for 40 elements. A 300-mg aliquot was pulverized for chemical analysis, and the magnetic fraction analyzed for silver, arsenic, gold, bismuth cadmium, cop­ was archived. Rocks were collected from prospects, altered per, molybdenum, lead, antimony, and zinc by ICP-AES/ zones, and outcrops within the study areas; examined DIBK (Motooka, 1988), a more sensitive method for most

012 Mineral Resources of the Wilderness Study Areas: Havasu Region, Arizona EXPLANATION

Rock, stream-sediment, or heavy-mineral­ Area containing anomalous levels of barium in concentrate sample collection site creosotebush or paloverde samples Vegetation and soil sample collection site­ Area containing anomalous levels of Specific elements detected in these samples molybdenum in creosotebush or paloverde are listed in text samples

Area containing anomalous concentrations of Sample site with anomalous levels of gold in 0 both creosotebush and paloverde samples elements shown 1 Sample site with anomalous levels of gold in Au, Ag Upper and lowercase letters denote elements creosotebush samples only detected in rock samples • Area containing anomalous amounts of Bacillus Lowercase letters denote elements detected in au, ag cereus spores in soil samples heavy-mmeral-concentrate samples

Listed minerals detected in either heavy­ malachite mineral-concentrate or rock samples Ag, silver; As, arsenic; Au, gold; Ba, Barium; Be, beryllium; Bi, bismuth; Cd, cadmium; Co, r:::::::l Area containing anomalous levels of copper in cobalt; Cu, copper; Fe, iron; Mn, manganese; ~ creosotebush or palo verde samples Mo, molybdenum; Pb, lead; Sb, antimony; Sn, tin; Sr, strontium; Th, thorium; W, tungsten; Zn, zinc-Same definitions apply to elements shown in lowercase letters

Figure 3. Geochemically anomalous areas in and near Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona, delineated using data from rock, heavy-mineral-concentrate, and vegetation samples and by Bacillus cereus spores detected in soils. Base from U.S. Geological Survey, 1:62,500, Black Peak, 1959; Bouse, Utting, 1962; Swansea, 1966. Contour intervals 20, 40, and 80 ft.

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 013 Table 4. Surl)mary statistics for anomalous concentrations of elements from rock, stream-sediment, heavy-mineral-concentrate, .creosotebush, and paloverde samples; and for Bacillus cereus spore counts from samples collected in and around Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona [See figure 3 for definition of element symbols. See Eppinger and others (1990a, b) for complete analytical data. Lower limits of detennination shown in parentheses. n, number of samples analyzed, N, not detected; L. detected but lower than detennination limit; G, greater than upper detennination limit. Analyses by emission spectrography, except for elements with "-a" or "-i" suffixes, which are by atomic absorption or inductively coupled plasma-atomic emission spectroscopy methods, respectively. Values in parts per million unless noted otherwise; pet, percent; ppb, parts per billion]

Element Minimum Maximum 50th Average Threshold Number of samples Percentile crustal above threshold abundance'

RCK:ks1 (n =33) Ag (0.5) N 5 N 0.07 1 6 As-i (1) N 170 7 1.8 20 11 Au-a (2 ppb) N 400ppb N 4ppb 20ppb 4 Ba (20) 100 3,000 500 425 2,000 6 Be (1) N 7 L 2.8 5 3 Bi-i (1) N 49 N 0.17 10 4 Cd-i (0.05) N 12 .25 0.2 10 2 Co (10) N 500 15 25 300 1 cu (5) L 10,000 20 55 300 6 Fe (.05 pet) 0.07 pet G 1.5 pet 20pet 2 Mn (10) 10 3,000 300 950 2,000 6 Mo (5) , N 30 N 1.5 5 9 Pb (10) N 200 15 13 50 3 Sb-i (1) N 32 L 0.2 5 3 Sr (100) N 5,000 200 375 2,000 3 Zn-i (0.05) 3.6 1,200 55 70 200 6

Nonmagnetic heavy-mineral concentrates~ (n=8)

Ag (1) N 1 L 1 Au (20) N L L 1 Ba(50) 4,000 G(lO,OOO) 6,000 G(lO,OOO) 3 Be(2) N 3 2 3 1 Sn (20) L 70 25 70 2 Th (200) N 500 L L 5

Weakly magnetic heavy-mineral concentrates~ (n = 8)

Fe (0.1 pet) 10pet 30pet 20pet 30pct 3 Mo (10) N 10 N L 4 Th(200) N L N L 2 w (50) N 70 N L 1 Zn(SOO) N 500 N L 1

Creosotebush (n = 98)

Au-a(1 ppb) N 6ppb 0.1 ppb <1ppb 11 Cu-a (0.1) 32 490 67 92 25 Ba-a (2) 170 1,300 590 760 23 Mo-a(0.3) 2.7 21 7.2 8.4 25 Bi-a (2) N 3.3 <2 <2 4

Blue paloverde (n = SS)

Au-a(l ppb) N 13ppb 0.1 ppb <1 ppb 13 Cu-a (0.1) 38 170 81 98 14 Ba-a (2) 190 2,000 760 800 26 Mo-a (0.3) .74 6.1 2.9 2.5 28

014 Mineral Resources of the Wilderness Study Areas: Havasu Region, Arizona Table 4. Summary statistics for anomalous elements from rock, stream-sediment, heavy-mineral concentrate, creosotebush, and paloverde samples; and for Bacillus . cereus spore counts from samples collected in and around the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County Ari~ona-Continued

Element Minimum Maximum 50th Average Threshold Number of samples Percentile crustal above threshold abundanceZ

Little-leaf paloverde (n =43)

Au-a(1 ppb) N 4ppb 0.1 ppb· <1 ppb 10 Cu-a (0.1) 34 120 73 65 27 Ba-a (2) 190 1,600 810 1,000 10 Mo-a (0.3) .39 7.2 1.1 2.0 10

Bacillus cereus spore counts (n =98)

counts/g (10) L 25,000 380 1,100 22 1 These data are derived from samples collected in areas 1-8 shown in figure 3. Areas 9 and 10 are excluded. 2 Data from Levinson (1980). of these ore-related elements. One-gram aliquots were ana­ study area (fig. 3) (Eppinger, 1990a, b). Anomalous con­ lyzed by a modified GFAA method of Meier (1980) to , centrations of elements were found in rock samples and in determine the ultralow concentrations of gold normally found the nonmagnetic and slightly magnetic heavy-mineral-con­ in plants. Though for plants the GFAA stated lower limit centrate samples. No anomalous concentrations of elements of determination for gold is 1 ppb, further work on a subset were found in stream-sediment samples. of these samples suggests that typical background gold con­ Samples of quartz veins cutting lower plate mylonitic centrations are about 0.1 ppb in the ash. gneiss collected from dumps near the Green Streak mine in ·Frequency distribution diagrams (hist.Qgrams) and cu­ area 1 (fig. 3) contain gold concentrations of 220 and 400 mulative frequency plots that show the general distribution ppb (Eppinger, 1990a, b) and 400 to 1,870 ppb (Kreidler, and range of the data were constructed for selected ele­ 1987). These rocks contain anomalous concentrations of ments. Boundaries between background and anomalous silver (1-5 ppm) and copper (1,500-10,000 ppm) and slightly element concentrations were chosen based on the crustal anomalous concentrations of arsenic, bismuth, antimony, abundarices for elements given by Levinson (1980). For molybdenum, lead, and zinc. the plant data, any detectable concentrations of gold, anti­ Six rock samples were collected from three outcrops mony, bismuth, and vanadium are considered anomalous. of lower plate mylonitic crystalline rocks in area 2, 1 mi Geochemical anomalies in rock, heavy-mineral-con­ south of the Green Streak mine. These rocks contain centrate, creosotebush, and paloverde samples and B. cereus anomalous concentrations of gold (1 sample, 30 ppb), cop­ spore counts in and around the study area are shown in per (as much as 7,000 ppm), molybdenum, lead, barium, figure 3. Summary statistics and thresholds for anomalous and strontium (Eppinger, 1990a, b). Thin quartz veins fol­ elements identified ~ samples from the study area are lowing shear zones cut the gneiss in this area. Oxidized listed in table 4. Rock and heavy-mineral-concentrate data pyrite boxwork and chrysocolla were observed in float of from samples collected in nearby mineralized areas, area 9 vein quartz. Two heavy-mineral-concentrate samples from in the northern Plomosa Mountains (fig. 3), and from area arroyos draining these outcrops contain anomalous concen­ 10 in the Pride mineral district (fig. 3) aided in identifying ttations of barium, iron, molybdenum, and tungsten. Bar­ suites of anomal9us element concentrations and thresholds ite, specularite, and fluorite are present in the nonmagnetic in metallic deposits in the region but are not included in the heavy-mineral-concentrate samples. data summary presented in table 4. No detailed follow-up No anomalous concentrations of metals were found geochemical studies of the anomalies identified in the study in three rock samples of tufa-capped basalt collected in area area have been undertaken. 3 (fig. 3). However, gold Oess than 20 ppb) was detected by emission spectrography in one heavy-mineral-concen­ trate sample collected· from an arroyo draining the north Rock, Stream-Sediment, and Heavy-Mineral-Concentrate side of an unnamed hill where the Osborne VABM (vertical­ Samples angle benchmark) is located (Eppinger, 1990a, b). The same sample contains anomalous concentrations of silver Rock, stream-sediment, and heavy-mineral-concentrate (1 ppm) and slightly anomalous concentrations of tin and samples were collected from outcrops in and around the thorium. No gold was observed in a mineralogical scan of

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 015 ilie lhleavy-mfumeml!-oollllcellllttmre §ample. A OOOOllll(!J lhle&vy­ coocenn:mtioJrns of mse~rnic, coppell", barium, manganese, and millllem.R-collllcoo~ ~pRe ooRRec!lOO lfrom oo mroyo dlrnnllll­ sttontillllm; Mdl sllighally arrnomallooo corrnceJrntlrations of molyb­ illllg ilie OOllllili si«ile 011' iliis lllm1l'W1Ill00 lhliRR OOllllWllllS ooom~OllllS dleJrnllllm, bismuruhl, lleOO!, mud! zD.n:nc (Eppfumgeir, 1990a, b). All

oollllcellllU:mtiolllls o11' Rrollll 9 lliJreC, mollyMellll1Ulllllll, oodl iliorillllm. sP.Jt lhleavy-mfumemll-collllreJrnltlraae ~plies collocredl RHll area 9 A JJOClk swmplle lfrom ioasWla croppfumg ooa illll me& 4 (fig. ooJrnurin anoHMl!olll!s coirncerrnltlrn.ltlio~rns of bmtlRm, sttontium, and 3) collllmfums ooomalloos coocennarnltliolllls of OOrillllm. Of ttwo mmugooese, oodl sevemll ~plies aliso contilin anomalous lhle&vy-mfumemll-collllcellllwre §amplles from me same ~ orrne coJrncerrnwtiolllls of wngst.ellll, moRyMenum, aJrsenic, and cop­ contmJrns ooom~oos collllceJrnU:mtioos of mollylbdleJrnllllm oodl ilie pell. Bmre lis abumd!M~ in heavy-mJiJrneir~-concentrate omeir oorrnttrulllls ooomallooo oorrncerrnttmtiorrns of lbmillllm oodl ilio­ samples. Ottl!Tleir mlinernlls mcliudle fluorite, specularite, py­ rillllm. A smallll M]01Ulllll& of sclhleelliire, a ttnmgsrellll-bearirrng millll­ ritte, COirlllllllldl\\lllfllll, oodl scllneeRite. emll, w~ obsenoo illll olllle llllOJrnmagrrnetic llneavy-mirrnernll-collll­ Samplies oolilecttedl lillll ~ 10 (fig. 3) ruse provide cellllttmre swmplle. P.rrnlfoirmatiollll Jfoir furnttelr]pretirrng nhe ~ from \the study area. Five ll'OClk SM"nplles were collllocred from smallll isoRaredl Nfume samples oif mP.rrnernlllizedl lioweir pllaae mylonitic gneiss Ollll~Irops of P~oowic memsedlimerrnmrry ll'OClis fum ~ 5 (fig. lfrom ltlhiJree ~(Pride 2Jrndl New S&oodlardl mines and Little 3). These Iroclis, collllecred ~orrng ill"ollll- oodl moogooese-oJt­ Golldlellll piriOOJ!reC~) conttrullll Momallouxs OOJrncentrations of gold idle-riclhl f~l1Ulllt mlllles, corrntilin ooomallolllls oorrncerrnttmtioJrns of (3 samplies, um pplb, 200 ppb, mud! 200 ppb), silver (3 sillveir, msellllic, bismllllili, coballa, mollyMemxm, lleadl, zmc, samplies mllllgmg from 1 \1o 2.1 ppm), arsenic, bismuth, anti­ irorrn, and! mMgrunese oodl sllightly ooomallous concenltlrations mony, coppell", coball~ and! iron ~ weiR as slightly anoma­ of Read!, lbecylllliillllm, arrndl cadmium (Eppirrngeir, 1990a, b). A lous conceJrnarn.tions ofau.mgsum (Eppmgeir, 1990a, b). Heavy­ single he&vy-mmem.li-oollllcentrat.e sample coU.ect.ed from \this minemll-co~rncentrnte samples (3 ttottll) contain anomalous area cona&Jrns mJ~omallmns corrnceJrnttmtioJrnS of ill"on arrndl sllighally co~rnce~rnttatiolllls of coppell", lieadl, aungsten, !barium, and rron anomallous OOllllCeJrnttmtiolllls of iliorillllm. Minern.lls ideJrntifiedl andlliesseir runmmas of iliorium. Mlineirals lin heavy-mineral­ .firm me JrnOJrnmagrrnetic lhle&vy-mmeJrall-OOJrnceJrnttat.e smnplle llllll­ conce~rnltlm.tte smnpRes P.JrncRudle calcitte, malachite, chrysocolla, dudle OOriae oodl aommalliiirne. oodlbmtte (Ewingeir, 1990a, 1b). Tmce amounts of galena Eiglhla Iroclk ~plles were oollllecaedl from basal!& Ollll&­ were dlerecaedl fum a samplle from ilie Pride mine area crops illll me& 6 (fng. 3). Thll"ee samplles, oollllecttedl from malachire-swrrnedl, qoortz-~ciae veim Cllllttirrng faullredl ba­ salla, oorrnwrrn dlerecaalblle golldl (6, 10, oodl 20 ppb) (Epp.iJrngeir, 199Da, b). Two goRdl-~g SIDJnplles aliso conttilrn anoma­ lous conceJrnttatiorrns of usenic oodl copper. Other rode samples illll abe mea oonmm Momallooo concentrations of GoRdl w~ d!et.ecttedl fum only 10 peircent of ilie creosote­ marrngaJrnese, banillllm, oodl slliighaly anomaimns corrnceJrntrn.tio~rns bush Mdl palloverr'dle samplles (Eppingeir, 1990~ b). The of moRyMemxm. A single bmae-riclhl, heavy-minemll-cmn­ maJdmum co~rnceJrntrations d!eteirminedl were 6 ppb for ceJrntrare sample from ttlhle mea contrins ooomallous coJrncellll­ creosorebuslhl, 13 ppb foir blue paioveirde, and 4 ppb for trn.timus of banillllm as wellll ~ sR.ighaly Momallous co~rnceJrnam­ Ritttle-liealf paloveirdle. Bocoose bacl\cgiroundl Revels appeair 1t0 ti.om; of lhecyllllium arrndl tillll. 100 aooua 0.1 lPJPlb, weHR lbeliow !tRue 1 pplb llimi~ of dletermina­ Two samples of c~ciae veiJrns weire ooHocttedl from tiollll, samples with d!et.ecttedl gold! are ooomalous, andl iliose birecd.attedl Mdlesitic llOCks illll area 7 (fig. 3). Anomallous slires wheire awo Oir more plana smnplies contAin d!etectablle concenltlrations of mMgarrnese, molybdenum, bismuah, and! golidl are especially noteworthy (fng. 3). The highest con­ arseJrnic oodl sRigllually arrnom~ous coJrncentrn.tions of zi~rnc and centtations of golidl were d!etecttedl nJrn the paloverde sample coppell" are pireseJrn& m ilie veins (Eppinger, 1990a, lb). firom site 35, where samplles of creosotebush and paloverde Ch!rysocona, m~aclluiae Mdl quartz me also presena in \the also conaain anomalous concentrations of barium and mo­ calcite veiJrns. RyMerium (fig. 3). Three samples of oodesitic volcarrnic Irocb were coll­ Coppell" anomaHes fum planas wiiliillll the swdly area are Recredl Jirrn area 8, wlhlnclhl mdudes ilie Blade Mmmmin mme. geJrneraHy Iresttictedl ao areas having mowHll coppell" occur­ An \three sru1rnpRes oonmfum sHglhtly ooomalous'concentrations re~rnces. Two exceptions are sites 16 and46 (fi.g. 3), where of siRveir (as muclhl as 1 ppm) arrndl two of ilie allruree oonmm ilieire me no outcirops. Sitte 46 is of particularr interes~ be­ anom~ous corrnceJrnltlratio~rns of msennc, antimoJrny, coppell", cause of oodlitio~ anomalous concentrations of gold! and barium, oodl s&Irorrntium. Barite, calldtte, oodl J11uoritte fom moRyMeJrnum lillll vegemtiollll oodllhecause of ilie high.B. cereMS part of ilie stteepRy ruwn~rng velins in ttllue mea. SJPOire colll!nt Coppell" is Irelativeny immobile in most arid Sevemll samples, collllocredl in area 9 (fig. 3), providle ellllvrroJrnmeJrnts and! is ilierefore reflected! m vegetation near additioJrnall mfomation for .maerpreting ilie dla~ from ilie ias smnrce. For e;mmple, Lovering and McCarthy (1978) stllldy mea. Nme minemliizedl rocl\c samples from pirospects Ireportedl \that ttwigs mulllieaves firom mesquite ttrees (Prosopis illll granitic MdlfeRsic vokooic rocb oontam gold 000 ppb sp.) that mp alllcaline ground wateir near the Sierrita, Ariz., and 1,200 ppb) Mdl sillveir 0 sample, 1 ppm); ooomalous coppell" oirebOOy OOJrnceJrntraredl moliyMenum but did not con- centrale copper. Yet similar samples of mesquite trees that cereus anomalies related to metal enrichment. Alternatively, grew on caprock in an acidic environment over an oxidiz­ perhaps this bacterium simply does not respond predictably ing pyritic copper orebody at Ray, Ariz., yielded strong to mineralized areas in this region. Nevertheless, the local­ copper anomalies. Thus, the anomalous concentrations of ity of the highest observed B. cereus spore count overlaps an copper in vegetation samples collected in the study area area where the creosotebush and paloverde contain anomalous probably indicate a nearby source. concentrations of metals (fig. 3). Analyses of creosotebush and blue paloverde revealed an extensive barium-rich zone in the south-central part of the Cactus Plain Wilderness Study Area. A cluster of four sites with particularly high levels in creosotebush lies im­ Interpretation mediately north of basalt in area 6 (fig. 3). Dunn and Hoffman (1986) found that plants growing over mineral­ Three suites of elements are found in anomalous con­ ized veins in the boreal forests of northern Saskatchewan centrations in rock and (or) heavy-mineral-concentrate contain unusually high concentrations of barium. Because samples from five mineralized bedrock areas at various lo­ of the shallow nature of the creosotebush roots, the barium­ calities around the Cactus Plain and East Cactus Plain Wil­ rich bedrock source may be near the surface. derness Study Areas (areas 1, 7, 8, 9, and 10; fig. 3). These In sharp contrast to the limited areas marked by are: (1) an anomalous silver-arsenic-bismuth-copper suite anomalous concentrations of copper, anomalous concentra­ in four of the five areas; (2) an anomalous gold-barium­ tions of molybdenum in the south-central part of the Cactus molybdenum-lead-antimony-zinc suite that is found in three Plain Wilderness Study Area (fig. 3) show a broad disper­ of the five areas; and (3) an anomalous tungsten-manga­ sion halo that is associated with locally mineralized outcrops nese-strontium suite that is found in two of the five areas. and with anomalous concentrations of copper and barium in Metals in anomalous concentrations in creosotebush plants. This broad molybdenum halo is consistent with the and paloverde from these five bedrock areas include gold, conclusions of Huff (1970), who delineated a widespread copper, molybdenum, and, in area 10, bismuth. Mineral area of anomalous concentrations of molybdenum in mes­ deposits in these areas are interpreted as being related to quite samples around known alluvium-covered copper de­ Tertiary detachment faults in the region (Spencer and Welty, posits in the Pima mining district of southern Arizona Prob­ 1986, 1989). Though bedrock is sparse, many of the ele­ ably because of such large dispersion halos for molybde­ ments of the previously described suites are found in num, Chaffee (1976) considers copper a more useful metal anomalous concentrations in rock and heavy-mineral-con­ for defining areas for detailed exploration, though molybde­ centrate samples collected within the study area. Areas 2, num is more useful in broad reconnaissance prospecting. 5, and 6 are noteworthy for being anomalous in at least 6 of Creosotebush samples from the Pride and New Standard the 13 elements. mines and the Little Golden prospect in area 10 (fig. 3) are Elements in anomalous concentrations in rocks and unique because they contain exceptionally high concentrations heavy-mineral-concentrate samples from area 2 most likely of copper and, more importantly, the only detectable amounts reflect areally extensive metal enrichment along shears and of bismuth in vegetation. These anomalous concentrations quartz veins in lower plate rocks related to the nearby min­ of bismuth mirror the bismuth-rich rocks of area 10. eralizing system in the Green Streak mine area. In area 2, the gold-barium-copper-molybdenum-lead-strontium-tung­ sten geochemical suite in rocks and heavy-mineral-concen­ trate samples, the occurrence of specularite, chrysocolla, Bacillus cereus fluorite, oxidized pyrite boxwork, and vein quartz in samples from isolated outcrops, and the large copper anomaly and Of the five mineralized areas sampled, only soils from local gold anomaly in vegetation suggest that similar de­ the New Standard mine (area 10, fig. 3) yielded high amounts posits to those in the Green Streak mine area may be con­ of B. cereus in spores (Eppinger, 1990a, b). Single-site B. cealed under alluvium surrounding the isolated bedrock. cereus anomalies were common, generally without associated The silver-arsenic-barium-beryllium-cadmium-cobalt­ anomalies in vegetation, rock, or heavy-mineral-concentrate molybdenum-lead-thorium-zinc suite in rocks and heavy­ samples. These facts, coupled with evidence of high within­ mineral-concentrate samples and the anomalous concentra­ site variability, diminish the usefulness of this microbiological tions of molybdenum in vegetation in area 5 were detected method, by itself, to assess the resource potential of the in samples collected along iron- and manganese-oxide-rich study area. Reasons are unclear for the general lack of B. faults cutting upper plate Paleozoic rocks. Most of these cereus anomalies in mineralized areas or for B. cereus metals are readily scavenged by iron and manganese ox­ anomalies without coincident anomalies in other sample ides, a process undoubtedly responsible for much of the media. Cattle activity throughout the region may have af­ metal enrichment. Nevertheless, the assemblage of metals fected bacterial populations enough to overshadow any B. is similar to that for detachment fault-related deposits. The

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 017 possibility that the~scavenged metals have been remobilized Geochemical anomalies in rock and heavy-mineral­ · and are derived from concealed deposits cannot be ruled out. concentrate samples in areas 3 and 4 may be related to a A silver-gold-barium-berylliwn-copper-molybdenum­ similar remobilization of underlying deposits, though these manganese-tin suite is found in area 6 in rock and heavy­ anomalies are less extensive, and associated veins or shears mineral-concentrate samples derived from postdetachment, were not observed. However, molybdenum and gold locally vented basalts. This assemblage and the occurrence anomali~s in vegetation are positive criteria for possible of chrysocolla and azurite in quartz and calcite veins along concealed deposits in these areas. faults suggest the possibility of leakage halos related to remobilization of metals in underlying detachment fault­ related deposits. Analyses of vegetation samples surround­ ing and east of area 6 yield widespread anomalous concen­ Geophysical Studies trations of barium and molybdenwn and local anomalous concentrations of copper and gold, including the highest The Cactus Plain and East Cactus Plain Wilderness ·gold concentrations in vegetation found in this study. Thus, Study Areas are covered by regional gravity anomaly data the leakage halos may be much more extensive than the (Lysonski and others, 1980; Aiken and others, 1981; De­ limited bedrock exposures in area 6 indicate. fense Mapping Agency Aerospace Center, 1974, 1975), re-

Figure 4. Bouguer gravity anomaly map of Cactus Plain and. East Cactus Plain Wilderness Study Areas, La Paz County, Arizona, and surrounding region. Contour interval, 1 milligal; grid interval, 1.5 km (5,000 ft); hachures in direction of gravity low. Squares denote observation points; see text for discussion of labeled anomalies.

018 Mineral Resources of the Wilderness Study Areas: Havasu Region, Arizona gional aeromagnetic anomaly data obtained in the National Inc., 1980). These data were merged to produce an aero­ Uranium Resource Evaluation (NURE) program (U.S. De­ magnetic map that covers a large region (fig. 5) and aero­ partment of Energy, 1979a, b; LKB Resources, Inc., 1980), magnetic maps that cover only the study area (figs. 6 and 7). and detailed aeromagnetic anomaly data (U.S. Geological The NURE magnetic anomaly data northeast of lat Survey, 1981) having sufficient resolution to defme anoma­ 34° N., long 114° W. were previously reprocessed (DeWitt lies of 1 mi2 or larger. Contours of complete (terrain-cor­ and others, 1988) and for this investigation were merged rected) Bouguer gravity anomalies are defined by about 45 mathematically with all other NURE data and reprocessed observation points, most of which immediately surround using algorithms and computer programs of the Branch of the study area (fig. 4). Contours of total-field magnetic Geophysics (1989). The resulting aeromagnetic data (fig. anomalies are defmed by five surveys having differing flight 6) show spatial relationships of broad anomalies defined by specifications. Northwest of lat 34° N., long 114° W., one sparse data of similar resolution and shows most impor­ survey was flown east-west at 0.5-mi spacing and 1,000 ft tantly if these anomalies continue across various aeromag­ altitude (U.S. Geological Survey, 1981) and another survey netic survey boundaries. The detailed U.S. Geological was flown east-west at 3-mi spacing and 400 ft altitude Survey aeromagnetic data northwest of lat 34° N., 114° W. (U.S. Department of Energy, 1979a). Northeast of this co­ (fig. 7), recompiled from original aircraft data for this in­ ordinate, lines were flown east-west at 1-mi spacing and vestigation, cover about 80 percent of the Cactus Plain Wil­ 400ft altitude (U.S. Department of Energy, 1979b). South­ derness Study Area and are useful for judging the quality of east and southwest of this coordinate, lines were flown east­ the sparse NURE data and for assessing in detail some west at 3 mi spacing and 400 ft altitude (LKB Resources, geologic sources of anomalies. For example, the

Figure 5. Residual total-intensity aeromagnetic map of the Whipple, Buckskin, and northern Plomosa Mountains, Arizona and California. Contour interval, 20 nanoteslas. Hachured in direction of lower values.

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 019 conspicuous highs at about lat 34° 10' N., long 114° 15' W. tus Plain Wilderness Study Area and is flanked by gravity (AI on fig. 6) and lat 34° 04' N., long 114° 12' W. (A2 on plateau GH3 at its north margin. Where the gravity anoma­ fig. 6) based on the NURE data are largely artificial but lies lie over bedrock, highs tend to be associated with high­ other anomalies are generally consistent with patterns shown density granitic and metamorphic rocks in the lower plates on the detailed map (fig. 7). of the detachment faults, whereas the lows tend to be asso­ ciated with low-density sedimentary rocks and sediments in a veneer or basin fill above the bedrock. Basin fill underly­ Gravity Data ing the region of low GL3 is inferred to have a maximum thickness of about 3,000 to 3,500 ft, consistent with esti­ The gravity anomaly map (fig. 4) shows that the study mates of Oppenheimer and Sumner (1980), on the basis of ~is surrounded by prominent lows to the east (GL1) and drillhole data and gravity modeling. Fill underlying GLI north (GL2) and by prominent highs to the west (GH1) and may have a maximum thickness of as much as 1,000 ft, . south (GH2). Data east and northeast of the study area are although this estimate remains highly uncertain because of sparse, limiting their usefulness for drawing specific con­ the sparseness of data. Where sedimentary rocks are over­ clusions about subsurface density contrasts. Between the lain or intruded by high-density basalt, the basalt is too highs~ low GL3 traverses the south-central part of the Cac- vesicular or too thin (small in volume) to increase signifi-

200 i_/ ...... Ht·/ /-- .. I .... ./ I I APPROX]MATEBOUNDARY OF EAST CACTUS PLAIN Wll.DERNESS STUDY

BOUNDARY OF CACTUS PLAIN 34o WILDERNESS 00' STUDY AREA (~-050-014-A/B)

1/ ·:>~) ~-..._, ) / / ! l' (§) //>"­ . / :... ___,/~~ :>--' I \ :>:::/: \ /'-., . / \ .· /'' ..\ \ . ',.

/ C) / '\ \ ' / :

/

Figure 6. Aeromagnetic anomaly map of. Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona, and surrounding region. Contour interval, 20 nanoteslas; grid interval, 1.5 km (5,000 ft); hachures in direction of lower anomaly values; dotted lines represent flightline traces; labeled anomalies discussed in text Compiled from National Uranium Resource Evaluation (NURE) program data.

020 Mineral Resources of the Wilderness Study Areas: Havasu Region, Arizona cantly the integrated density and gravity response. Rocks tus Plain Wilderness Study Areas reveals four pertinent fea­ of greatest density in and near the study areas are local tures (fig. 5). (1) A striking contrast in magnetic expres­ occurrences of specularite .breccia, massive iron oxide, and sion is evident between the postextension volcanic rocks, sulfide-bearing breccia in the detachment faults and related chiefly basalts, that produce intense short-wavelength high-angle faults in the upper plate. Though these rocks anomalies and the rocks affected by the extensional defor­ have bulk densities that range from about 3.0 to 3.8 g/cm3 mation that produce much more subdued and longer wave­ (grams per cubic centimeter), their volumes are too small to length anomalies. The boundary between these two mag­ generate highs observable on the regional gravity anomaly netic domains traces out an arc of a circle centered on the map. These high-density rocks could only~ detected and southeast comer of the map. (2) Within the terrane lacking followed in the subsurface by detailed gravity profiles hav­ postextension rocks, the aeromagnetic data traces out long ing a spac.ing no larger than about 25 ft. wavelength, northeast-trending anomaly highs and lows that correspond approximately to corrugations associated with the detachment fault, where the mylonitic rocks in the lower Aeromagnetic Data plate crop out in antiformal arches and the faulted rocks in The residual total-intensity aeromagnetic field for the the upper plate crop out in synformal troughs (Spencer and 800 mil region surrounding the Cactus Plain and East Cac- Reynolds, 1989a). Metallic mineral deposits are commonly

Figure 7. Aeromagnetic anomaly map of a region northwest of lat 34° N., long 1 14° W. that includes part of the Cactus Plain Wilderness Study Area, La Paz County, Arizona. Contour interval, 20 nanoteslas; grid interval, 0.25 km (800 ft); hachures in direction of lower anomaly values; dotted lines represenrflightline traces. Compiled from U.S. Geological Survey data.

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 021 preserved in the ttoughs (Spencer and Welty, 1989). The small flightline spacing of this survey permits develop­ broad anomaly trends associated with lower plate corruga­ ment of maps showing where boundaries of buried mag­ tions cannot be ttaced through the belt of short-wavelength netic rocks are likely to be present (Branch of Geophysics, anomalies produced by the postextension basaltic rocks 1989). Such maps showing crest lines and points of maxi­ concealed beneath Cactus Plain. (3) Northwest-trending mum horizontal gradients of pseudogravity anomalies were gradients within the aeromagnetic data cut across the north­ prepared and used, in part, to estimate the subsurface hori­ east-trending highs and lows. Where these gradients over­ zontal extent of magnetic rocks. lie bedrock, they correspond to northwest-trending high­ Postdetachment sediment and sedimentary rock cov­ angle faults. Therefore, buried northwest-trending faults ering the extended upper plate and lower plate rocks is a can be inferred in areas of alluvial rover. (4) An area of thin veneer less than 500 ft thick, except where it is inferred strong field disturbances on the southern margin of the map to thicken to as much as 3,500 ft on the basis of the gravity overlies the Bouse Hills, where Proterozoic, Mesozoic, and low's magnitude. Therefore, any mineral occurrence that Tertiary volcanic, plutonic, and metamorphic rocks crop might be postulated to occur near the detachment surface out would be generally accessible for recovery, except in the The NURE aeromagnetic anomaly map (fig. 6) shows region of thickened sedimentary cover, such as in the south­ that a northwest-trending belt of anomalies, primarily highs western to south-central parts of Cactus Plain Wilderness (MH1, MH2, MH3, and MH4}, ttaverses the center of the Study Area (area of GL3 on ·fig. 4). Such accessibility Cactus Plain Wilderness Study Area, extending from are­ might be somewhat hindered, however, by the presence of gion capped by basalt north of the study area (MH1) to a basalt at shallow depths in a northwest-trending belt that region of granitic and metamorphic rocks south of the study ttaverses · the central part of the study area (area of GH3, area (MH4). The map also shows that small-amplitude fig. 4). highs are generally associated with granitic and metamor­ The specularite breccia, of perhaps greatest interest phic rocks (MH5, MH6, and MH7 and probably MH8 and because similar rocks contain abundant gold at the Copper­ MH9) and that large-amplitude highs are associated with stone mine 10 mi to the southwest, is sufficiently dense to basalt (MH1 and probably MH2 and MH3). Trachytic and be detected and followed in the subsurface, provided that rhyolitic flows and tuffs adjoining the study areas on the very detailed, high-precision gravity surveys are made. This north (ML1), volcanic and sedimentary rocks of the Bouse breccia, though weakly magnetic, could probably be de­ Hills south of the study area, and sedimentary rocks of the tected and followed by high-precision, ground-based mag­ Bouse Formation in and east (ML2) of the study area do netic gradiometer surveys. not generate significant anomalies and are inferred to be only slightly magnetic. The specularite breccia, massive iron oxide (mostly hematite), and sulfide-bearing breccia of pre­ viously noted high density have only weak magnetizations Natural Radioelement Data and are not aeromagnetic anomaly producers. The U.S. Geological Survey aeromagnetic anomaly Natural radioelement distributions in the Cactus Plain map (fig. 7) shows that the broad NURE anomalies of the ~d East Cactus Plain Wilderness Study Areas were evalu­ northwest-trending belt consist of numerous local highs ated by examination of available data from aerial gamma­ and lows; these highs and lows reflect in detail structural ray spectrometry surveys of the Needles (U.S. Deparunent trends of basaltic flows and intrusions, probable occurrences of Energy, 1979a) and Prescott (U.S. Department of Energy, of reversed or anomalously directed total magneti~tion 1979b) 1o by 2° quadrangles. These surveys acquired aerial (sum of induced remnant magnetization) of basalt, local gamma-my spectrometry data along 3-mi (Needles) and 1- variations of basalt-covered topography, and subtle changes mi-spaced (Prescott) east-west flightlines at 400 ft above in basalt thickness. For example, short-wavelength lows ground level. Three flightlines cross the part of the study are typically larger in amplitude than short-wavelength area within the Needles quadrangle and have about 5 per­ highs, and many of these lows do not appear north of cent ground coverage, because an aerial gamma-ray system counterpart highs, as would be expected if the total mag­ at 400 ft above ground level effectively measures terrestrial netization were normally directed. Of significance are the gamma radiation in an 800-ft-wide swath along the flight­ short-wavelength anomalies that indicate basalt is pervasive line. Six flightlines cross the part of the study area within at shallow depth beneath a cover of sand dunes at least as the Prescott quadrangle and provide about 15 percent ground far south as lat 34° N. Furthermore, both maps, when coverage. The respective 5 percent and 15 percent cover­ considered together, indicate that the belt of anomalies is ages represent a reconnaissance sampling of the near-sur­ caused by a combination of basalt and older granitic and face (0- to 18-in. depth) distribution of the natural radioele­ metamorphic rocks and that the granitic and metamorphic lnents potassium (K), uranium (eU), and thorium (eTh). rocks may underlie basalt in the northern part of the Cactus The prefiX "e" for equivalent denotes the potential for dis­ Plain Wilderness Study Area (near GH1, fig. 4). The equilibrium in the uranium and thorium decay series.

022 Mineral Resources of the Wilderness Study Areas: HavasU Region, Arizona Radioelement contour maps indicate that the study Several mines have also produced gold and silver, either as area is characterized by radioelement concentrations of 0.8 primary commodities or as by-products. The mines are to 2 percent K, 1 to 3 ppm eU, and 5 to 10 ppm eTh. developed in replacement deposits in carbonate rocks, in Higher concentrations of 2 to 3 ppm eU and 7.5 to 10 ppm epithermal veins in faults, in veins, and in replacement eTh are present in the eastern part of the study area and deposits localized in high- and low-angle faults in and above probably reflect a relatively greater abundance of uranium­ the detachment faults (Spencer and Welty, 1989). The Moon and thorium-bearing minerals in eolian deposits. For the Mountains detachment fault in the northern Dome Rock study area, the concentrations detected are thought to be of Mountains underlies the Copperstone mine, the largest pro­ reasonable (not anomalous) level for the eolian deposits ducer of gold in Arizona (Spencer and others, 1988). Other and other sedimentary rocks of the Bouse Formation that past productive mines are along the Buckskin-Rawhide compose most of the surface material. Radioelement con­ detachment fault system in the Buckskin Mountains centrations could not be determined for sparse outcrops of (Cienega, Mammon, Pride, and Midway mineral districts) older sedimentary, metamorphic, and igneous rocks. and in the Plomosa Mountains (Northern Plomosa mineral district). All the deposits are associated with detachment faults that project beneath the study area. Mineral Resource Potential On the basis of regional occurrences of metallic min­ eral deposits, Spencer and others (1988) and Spencer and To assess the mineral resource potential of the Cactus Welty (1989) argued that the Cactus Plain and East Cactus and East Cactus Plain Wilderness Study Area. regional ge­ Plain Wilderness Study Areas must be classified as having ology, geochemistry, geophysics, mineral occurrence maps, a high resource potential for gold, silver, copper, lead, and mining claim records, and available ore deposit models ap­ zinc. The geochemical and geophysical data obtained in plicable to geologic terrane in the region were studied. Be­ this study support this appraisal. This appraisal, however, cause much of the study area is covered by unmineralized ignores the economic problems for any future development sedimentary rock, biogeochemical and geophysical data are of potential ore deposits resulting from local significant the most useful in assessing the mineral resource potential. thickness (greater than 300 ft) of postmineralization basalts An estimate of the level of resource potential and degree of and sedimentary rocks that underlie parts of the study area. certainty for each tract was made using criteria outlined in Following Spencer and others (1988) and Spencer and the "Appendixes." Throughout this discussion, mineral re­ Welty (1989), the entire study area is assigned high potential source potential refers only to undiscovered mineral re­ for gold, silver, copper, lead, and zinc. Three specific areas sources. have a certainty level of D, whereas the remaining parts of Areas having mineral resource potential for gold, sil­ study area have a certainty level of B (fig. 2). The three ver, copper, lead, zinc, barite, fluorite, manganese, beryl­ areas with a certainty level of D are immediately south­ lium, and uranium resources were delineated. Applicable west of the Green Streak mine along the northeast border of metallic ore deposit models for the study areas include de­ the East Cactus Plain Wilderness Study Area, in the north­ tachment fault-related base- and precious-metal deposits western part of the Cactus Plain Wilderness Study Area, (Wilkins and Heidrick, 1982; Wilkins and others, 1986; and in the southeastern part of the Cactus Plain Wilderness Spencer and Welty, 1986, 1989; Spencer and others, 1988), Study Area. The certainty of level D is based primarily on stratabound and fault controlled manganese deposits (Spen­ geochemical data and the presence of the sparse bedrock cer and Welty, 1986), and stratabound uranium and vana­ outcrops in the area. Two other observations support the dium deposits (Sherbourne and others, 1979; Cox and Singer, certainty level assignment; these are ( 1) most metallic de­ 1986; Spencer and Welty, 1986). Some areas have re­ posits in the extended terrane are preserved within the syn­ source potential for sand and bentonitic clay. formal troughs where the upper plate rocks have not been removed by erosion and (2) the aeromagnetic data, which suggest that these synformal troughs project into the study area. Base and Precious Metals

Base- and precious-metal mines and prospects adjacent to the Cactus Plain and East Cactus Plain Wilderness Study Barite and Fluorite Areas have been worked intermittently since the late 1800's (Keith, 1978; Keith and others, 1983a, b). The mineral Barite and fluorite have been produced locally from occurrences are epithermal and contain iron-bearing miner­ mines in the Northern Plomosa and Bouse mineral districts als, usually specularite and less commonly pyrite, chalcopy- · (Stewart and Pfister, 1960; Keith, 1978). These minerals rite, and magnetite. Most mines have produced copper and are in veins and faults in upper plate Tertiary volcanic and lesser amounts of lead and zinc (Spencer and Welty, 1989). sedimentary rocks adjoining the southern edge of the Cactus

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 023 Plain Wilderness Study Area. Stream-sediment and bio­ Beryllium geochemical data in this area indicate a large halo of barium enrichment around these deposits. Because of these min­ Trace amounts of beryllium are present in manganese eral occurrences and the geochemical anomalies, this area ore produced from the southwestemmost Bouse Hills (Keith, is assigned high resource potential with a certainty level of 1978). The mines are developed in· northwest-trending D for barite and fluorite (fig. 2). fractures and faults that cut Tertiary volcanic rock. The Geochemical data from stream-sediment and rock faults are in the upper plate of the detachment fault The samples indicate the possible presence of unexposed barite association of trace beryllium with manganese ore and in the northwestern part of the Cactus Plain Wilderness anomalous concentrations of beryllium are the basis for two Study Area. Because of the lack of exposed mineralized areas in the northwestern and southeastern parts of the Cac­ ground, this area is assigned a moderate potential for barite tus J>lain Wilderness Study Area being assigned low poten­ with a certainty level of C (fig. 2). There is no .evidence tial for beryllium, certainty level B. available to assess the mineral resource potential of fluorite in this area.

Bentonitic Clay Manganese A few hundred tons of bentonitic clay were produced Mines in the Northern Plomosa and Bouse mineral for local drilling muds from sedimentary horizons adjacent districts have produced small amounts of manganese to the Bouse Hills (Wilson and Roseveare, 1949; Keith, (Farnham and Stewart, 1958; Keith, 1978). The deposits 1978). The deposits are in subhorizontal beds that are re­ are in high-angle faults cutting the unmetamorphosed upper ported to be altered tuffaceous sedimentary rocks. Tuf­ plate Tertiary volcanic and sedimentary rocks. Outcrops of faceous horizons are found in the region within the highly upper plate Tertiary volcanic and sedimentary rocks are faulted and extended volcanic rocks, in postdetachment tra­ only in, or adjoining, the southeastern part of and northwest chytic and rhyolitic volcanic centers, and as horizons in the corner of the Cactus Plain Wilderness Study Area. There­ Bouse Formation. On the basis of these occurrences, the fore, the southeastern comer in the Cactus Plain Wilderness entire study area is assigned low resource potential with a Study Areas is assigned moderate resource potential for certainty level of B for bentonitic clay (fig. 2). manganese with a certainty level of C because of the past production of manganese from nearby areas. The north­ western comer of the Cactus Plain Wilderness Study Area also is assigned moderate potential, though with a certainty Sand level of B because no occurrences of manganese are known in this area (fig. 2). Extensive eolian sand covers the southern three-quar­ ters of the East Cactus Plain Wilderness Study Area and the northern half of the Cactus Plain Wilderness Study Area. Uranium As noted previously, this sand is unsuitable for use in glass production though it is suitable for foundry, fracturing, and Scarborough and Wilt (1979) noted weak evidence abrasive materials. These areas are assigned high resource for uranium mineralization along a low-angle fault separat­ potential with a certainty level of D for sand (fig. 2). ing middle Tertiary limestone from crystalline rocks north of Osborne Wash. These moderately to steeply dipping rocks were deformed during extensional deformation. Ura­ nium occurs in the middle Tertiary sedimentary rocks else­ Oil and Gas where in the extended terrane of this region (Welty and others, 1985). Most notable is uranium at the Anderson Despite a significant number of oil and gas leases and mine in the Date Creek Basin about 40 mi to the northeast lease applications, the Cactus Plain and East Cactus Plain (Sherbourne and others, 1979). The association of uranium Wilderness Study Areas have no resource potential for oil with Tertiary sedimentary rocks suggests that the two areas and gas with a certainty level D. This assignment is justi­ in the northwestern and southeastern parts of the Cactus fied because of the general lack of hydrocarbon-bearing Plain Wilderness Study Area where these rocks crop out source or reservoir rocks, because of the abundance of have low potential with a certainty level of B for uranium metamorphic rocks in the ranges surrounding the study area, (fig. 2). The presence of thorium in the geochemical data and because the unmetamorphosed rock, where present in supports this assessment the region, generally forms thin deposits (fig. 2).

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026 Mineral Resources of the Wilderness Study Areas: Havasu Region, Arizona American Association of Petroleum Geologists Bulletin. v. 63, U.S. Geological Survey, 1981, Aeromagnetic map of the Needles p. 621-646. 1° by 2° quadrangle, California and Arizona: U.S. Geologi­ Spencer, J.E., compiler, 1989, Compilation geologic map of the cal Survey Open-File Report 81-85, scale 1:250,000. Buckskin and Rawhide Mountains, west-central Arizona, in U.S. Department of Energy, 1979a, Aerial radiometric and mag­ Spencer, J.E., and Reynolds, S.J. ed., Geology and mineral netic survey, Needles National Topographic Map, California resources of the Buckskin and Rawhide Mountains, west­ and Nevada: U.S. Department of Energy, Report GJBX- central Arizona: Arizona Geological Survey Bulletin 198, 114(79), v. 2. scale 1: 100,000. 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Welty, J.W., Spencer, I.E., Allen, G.B., Reynolds, S.J., and Trapp, --1989c, Tertiary structure, stratigraphy, and tectonics of the R.A., 1985, Geology and production of Middle Tertiary min­ Buckskin Mmmtains, in Spencer, J.E., and Reynolds, S.J., edS., eral districts in Arizona: Arizona Bmeau of Geology and Geology and mineral resources of the Buckskin and Rawhide Mineral Technology Open-File Report 85-1,88 p. Mountains, west-central Arizona: Arizona Geological Sur­ Wilkins, Joe, Jr., and Heidrick, T.L., 1982, Base and precious vey Bulletin 198, p. 103-167. metal mineralization related to low-angle tectonic featl.D'es in Spencer, I.E., and Welty, J.W., 1986, Possible controls of base­ the Whipple Mountains, California, and Buckskin Mountains, and precious-metal mineralization associated with Tertiary Arizona, in Frost, E.G., and Martin, D.L., eds., Mesozoic­ detachment faults in the lower Colorado River trough, Ari­ Cenozoic tectonic evolution of the Colorado River region, zona and California: Geology, v. 14, p. 195-198. California, Arizona, and Nevada: San Diego, California, --1989, Geology of mineral deposits in the Buckskin and Cordilleran Publishers, p. 182-203. Rawhide Mmmtains, in Spencer, J.E., and Reynolds, S.J., eds, Wilkins, Joe, Jr., Beane, R.E., and Heidrick, T.L., 1986, Mineral­ Geology and mineral resources of the Buckskin and Rawhide ization related to detachment faults: a model, in Beatty, Bar­ Mountains, west-central Arizona: Arizona Geological Sur­ bara, and Wilkinson, P.A.K., eds., Frontiers in geology and vey Bulletin 198, p. 223-254. ore deposits of Arizona and the southwest: Tucson, Arizona Spencer, J.E., Duncan, J.T., and Burton. W.D., 1988, The Copper­ Geological Society Digest, v. 16, p. 108-117. stone mine: Arizona's new gold producer: Arizona Bureau Wilkins, Joe, Jr., and Heidrick, T.L., 1982, Base and precious of Geology and Mineral Technology Fieldnotes, v. 18, no. 2, metal mineralization related to low-angle tectonic featl.D'es in p.1-3. the Whipple Mountains, California, and Buckskin Mountains, Stewart, L.A., and Pfister, A.J., 1960, Barite deposits of Arizona: Arizona, in Frost, E.G., and Martin, D.L., eds., Mesozoic­ U.S. Bureau of Mines Report of Investigations 5651, 89 p. Cenozoic tectonic evolution of the Colorado River region. Suneson, N.H., and Lucchitta, Ivo, 1979, K/Ar ages of Cenozoic California, Arizona, and Nevada: San Diego, California, volcanic rocks, west-central Arizona: Isochron/West, no. 24, Cordilleran Publishers, p. 182-203. p. 25-29. Wilkinson, W.H., Wendt, C.J., and Dennis, M.D., 1988, Gold --1983, Origin of bimodal volcanism, southern Basin and mineralization along the Riverside detachment fault, River­ Range province, west-central Arizona: Geological Society of side County, California, in Schafer, R.W., Cooper, J.J., Vikre, America Bulletin, v. 94, p. 1005-1019. P.O., eds., Bulk mineable precious metal deposits of the Thompson. C.E., Nakagawa, H.M, and Van Sickle, G.H., 1968, western United States: Reno, Nevada, Geological Society of Rapid analysis for gold in geologic materials, in U.S. Geo­ Nevada, p. 487-503. logical Survey Research, 1968: U.S. Geological S\lrvey Pro­ Wilson, E.D., and Roseveare, G.H., 1949, Arizona nonmetallics, fessional Paper 600-B, p. B130-132. 2d ed. rev.: Arizona Bureau of Mines Bulletin 155, 60 p. U.S. Bureau of Mines and U.S. Geological Survey, 1980, Prin­ Zambrano, Elias, 19~5. Geology of the Cienega mining district, ciples of a resource/reserve classification for minerals: U.S. northwestern Yuma Co\Dlty, Arizona: Rolla, University of Geological Survey Circular 831, 5 p. Missouri, M.S. thesis, 64 p.

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 027 APPENDIXES DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL AND CERTAINTY OF ASSESSMENT

LEVELS OF RESOURCE POTENTIAL

H HIGH mineral resource potential is assigned to areas where geologic, geochemical, and geophysical char-: acteristics indicate a geologic environment favorable for resource occurrence, where interpretations of data indicate a high· degree of likelihood for resource aq:umulation, where data support mineral-deposit models indicating presence of resources, and where evidence indicates that mineral concentration has taken place. Assignment of high resource potential to an area requires some positive knowledge that mineral-forming processes have been active in at least part of the area. M MODERATE mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of' data indicate reasonable likelihood for resource accumulation, and (or) where an application of mineral-deposit models indicates favorable ground for the specified type(s) of deposits. L LOW mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics define a geologic environment in which the existence of resources is permissive. This broad category embraces areas with dispersed but insignificantly mineralized rock, as well as areas with little or no indication of having · been mineralized. · N NO mineral resource potential is a category reserved for a specific type of resource in a well-defined area. U UNKNOWN mineral resource potential is assigned to areas where information is inadequate to assign a low, moderate, or high level of resource potential.

LEVELS OF CERTAINTY

A Available information is not adequate for determination of the level of mineral resource potential. B Available information only suggests the level of mineral resource potential. C Available information gives a good indication of the level of mineral resource potential. D Available· information clearly defines the level of mineral resource potential.

A B c D U/A H/B H/C H/D

HIGH POTENTIAL HIGH POTENTIAL HIGH POTENTIAL

l...J < fv\/B i= tvVC fv\/D z I.U MODERATE POTENTIAL MODERATE POTENTIAL MODERATE POTENTIAL bc.. UNKNOWN POTENTIAL uI.U o=: UB uc UD :::> 0 LOW POTENTIAL LOW POTENTIAL LOW POTENTIAL V) I.Uo=: u.. 0 N/D ...J I.U NO POTENTIAL I.U> ...J

LEVEL OF CERTAINTY

Abstracted with minor modifications from:

Taylor, R.B., and Steven, T.A., 1983, Definition of mineral resource potential: Economic Geology, v. 78, no. 6, p. 1268-1270. Taylor, R.B., Stoneman, R.J., and Marsh, S.P., 1984, An assessment of the mineral resource potential of the San Isabel National Forest, south-central Colorado: U.S. Geological Survey Bulletin 1638, p. 40-42. Goudarzi, G.H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. Geological Survey Open-File Report 84-0787, p. 7, 8.

030 Mineral Resources of Wilderness Study Areas: Havasu Region, Arizona RESOURCE/RESERVE CLASSIFICATION

IDENTIFIED RESOURCES UNDISCOVERED RESOURCES Demonstrated Probabi Iity Range Inferred Measured Indicated Hypothetical Speculative

I I Reserves Inferred ECONOMIC Reserves ____ .!.. _____ I I f------~ -~- Inferred MARGINALLY Marginal Marginal Reserves ECONOMIC Reserves I I ----,----1------~ -~- Demonstrated Inferred SUB- Subeconomic Subeconomic ECONOMIC Resources Resources I I I

Major elements of mineral resource classification, excluding reserve base and inferred reserve base. Modified from McKelvey, V.E., 1972, Mineral resource estimates and public policy: American Scientist, v. 60, p. 32-40; and U.S. Bureau of Mines and U.S. Geological Survey, 1980, Principles of a resource/reserve classification for minerals: U.S. Geological Survey Circular 831, p. 5.

Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona 031 GEOLOGIC TIME CHART Terms and boundary ages used by the U.S. Geological Survey in this report

AGE ESTIMATES OF EON ERA PERIOD EPOCH BOUNDARIES IN MILLION YEARS {Ma) Holocene Quaternary 0.010 Pleistocene 1.7 Neogene Pliocene 5 Cenozoic Subperiod Miocene 24 Tertiary Oligocene Paleogene 38 Eocene Sub period 55 Paleocene 66 Late Cretaceous f---- 96 Early 138 Late. Meso"zoic jurassic Middle Early 205 Late Triassic Middle Early -240 Late Permian Phanerozoic Early 290 Late Pennsylvanian Middle Carboniferous Early Periods -330 Late Mississippian Early 360 Late Devonian Middle Paleozoic Early 410 Late Silurian Middle Early 435 Late Ordovician Middle Early 500 Late Cambrian Middle Early 1-570 Late Proterozoic 900 Proterozoic Middle Proterozoic 1600 Early Proterozoic 2500 Late Archean 3000 Middle Archean Archean 3400 Early Archean ------{3 8001)------pre-Archean2 4550 'Rocks older than 570 Ma also called Precambrian, a time term without specific rank. 21nformal time term without specific rank.

032 Mineral Resources of Wilderness Study Areas: Havasu Region, Arizona Mineral Res.ources of Wilderness Study Areas: Havasu Region, Arizona

This volume was published as separate chapters A-D

U.S. GEOLOGICAL SURVEY BULLETIN 1704 U.S. DEPARTMENT OF THE INTERIOR MANUEL LUJAN, jR., Secretary

U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director CONTENTS

[Letters designate the separately published chapters]

(A) Mineral Resources of the Mohave Wash Wilderness Study Area, Mohave County, Arizona, by James G. Evans, David R. Sherrod, Randa11 H. Hill, Robert C. Jachens, and John R. McDonnell, Jr. (B) Mineral Resources of the Gibraltar Mountain and Planet Peak Wilderness Study Areas, La Paz County, Arizona, by Robert G. Eppinger, Jocelyn A. Peterson, H. Richard Blank, Jr., K. Eric Livo, Daniel H. Knepper, Jr., James A. Pitkin, Jon E. Spencer, Stephen J. Reynolds, Michael J. Grubensky, Terry J. Kreidler, and David C. Scott (C) Mineral Resources of the Swansea Wilderness Study Area, La Paz and Mohave Counties, Arizona, by Richard M. Tosdal, Robert G. Eppinger, H. Richard Blank, Jr., Daniel H. Knepper, Jr., Andrea J. Gallagher, James A. Pitkin, Stephanie L. Jones, and GeorgeS. Ryan. (D) Mineral Resources of the Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona, by Richard M. Tosdal, Robert G. Eppinger, James A. Erdman, William F. Hanna, James A. Pitkin, H. Richard Blank, Jr., Richard M. O'Leary, John R. Watterson, and Terry J. Kreidler.

0 " SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS

Periodicals Coal Investigations Maps are geologic maps on topographic or planimetric bases at various scales showing bedrock or surficial geol­ Earthquakes & Volcanoes (issued bimonthly). ogy, stratigraphy, and structural relations in certain coal-resource areas. Preliminary Determination or Epicenters (issued monthly). Oil and Gas Investigations Charts show stratigraphic information for certain oil and gas fields and other areas having petroleum potential. Technical Books and Reports Miscellaneous Field Studies Maps are multicolor or black-and­ white maps on topographic or planimetric bases on quadrangle or ir­ Professional Papers are mainly comprehensive scientific reports of regular areas at various scales. Pre-1971 maps show bedrock geology wide and lasting interest and importance to professional scientists and en­ in relation to specific mining or mineral-deposit problems; post-1971 gineers. Included are reports on the results of resource studies. and of maps are primarily black-and-white maps on various subjects such as topographic, hydrologic, and geologic investigations. They ~o mcl~de environmental studies or wilderness mineral investigations. collections of related papers ad~essing different aspects of a smgle scien­ Hydrologic Investigations Atlases are multicolored or black-and­ tific topic. white maps on topographic or planimetri"' bases presenting a wide range Bulletins contain significant data and interpretations that are of last­ of geohydrologic data of both regular and irregular areas; principal scale ing scientific interest but are generally more limited in scope or is 1:24,000 and regional studies are at 1:250,000 scale or smaller. geographic coverage than Professional Papers. They include the results of resource studies and of geologic and topographic investigations; as well as collections of short papers related to a specific topic. Water-Supply Papers are comprehensive reports that present sig­ Catalogs nificant interpretive results of hydrologic investigations of wide interest Permanent catalogs, as well as some others, giving comprehen­ to professional geologists, hydrologists, and engineers. The series covers sive listings of U.S. Geological Survey publications are available under investigations in all phases of hydrology, including hydrogeology, the conditions indicated below from the U.S. Geological Survey, Books availability of water, quality of water, and use of water. and Open-File Reports Section, Federal Center, Box 25425, Denver, Clr'culars present administrative information or important scientific CO 80225. (See latest Price and Availability List.) information of wide popular interest in a format designed for distribution "Publications of the Geological Survey, 1879-1961" may be pur­ at no cost to the public. Information is usually of short-term interest. chased by mail and over the counter in paperback book form and as a Water-Resources Investigations Reports are papers of an interpre­ set of microfiche. tive nature made available to the public outside the formal USGS publi­ "Publications of the Geological Survey, 1962-1970" may be pur­ cations series. Copies are reproduced on request unlike formal USGS chased by mail and over the counter in paperback book form and as a publications, and they are also available for public inspection at set of microfiche. depositories indicated in USGS catalogs. 0 "Publications or the U.S. Geological Survey, 1971-1981" may be Open-File Reports include unpublished manuscript reports, maps, purchased by mail and over the counter in paperback book form (two and other material that are made available for public consultation at volumes, publications listing and index) and as a set of microfiche. depositories. They are a nonpermanent form of publication that may be Supplements for 1982, 1983, 1984, 1985,1986, and for subsequent cited in other publications as sources of information. years since the last permanent catalog may be purchased by mail and over the counter in paperback book form. Maps State catalogs, "List of U.S. Geological Survey Geologic and Water-Supply Reports and Maps For (State)," may be purchased by mail Geologic Quadrangle Maps are multicolor geologic maps on and over the counter in paperback booklet form only. topographic bases in 7 1/2- or 15-minute quadrangle formats (scales main­ 0 "Price and A vailablllty List or U.S. Geological Survey Publica­ ly 1:24,000 or 1:62,500) showing bedrock. surficial, or engineering geol­ tions," issued annually, is available free of charge in paperback book­ ogy. Maps generally include brief texts; some maps include structure let form only. and columnar sections only. Selected copies or a monthly catalog "New Publications of the U.S. Geophysical Investigations Maps are on topographic or planimetric Geological Survey" available free of charge by mail or may be obtained bases at various scales; they show results of surveys using geophysical over the counter in paperback booklet form only. Those wishing a free techniques, such as gravity, magnetic, seismic, or radioactivity, which subscription to the monthly catalog "New Publications of the U.S. reflect subsurface structures that are of economic or geologic significance. Geological Survey" should write to the U.S. Geological Survey,. 582 Many maps include correlations with the geology. National Center, Reston, VA 22092. Miscellaneous Investigations Series Maps are on planimetric or topographic bases of regular and irregular areas at various scales; they Note.--Prices of Government publications listed in older catalogs, · present a wide variety of format and subject matter. The series also in­ announcements, and publications may be incorrect. Therefore, the cludes 7 1!2-minute quadrangle photo geologic maps on planimetric bases prices charged may differ from the prices in catalogs, announcements, which show geology as interpreted from aerial photographs. Series also and publications. includes maps of Mars and the Moon. -~-~rosdal; other~~~_!RAL RE?OURCES, CAS"fUS AND E. CACfUS PLAIN WILDERNESS STUDY AREAS, ARIZONA-U.S.